Epidemiology: The beginning of wisdom in Public Health
An inaugural Lecture delivered at the University of Lagos Main Auditorium
on 10th August, 2016
By
Professor Ekanem E. Ekanem
BS (Nebraska), MPH, PhD (Texas), C. Stat (Belgium), FRSPH (UK)
Professor of Epidemiology
College of Medicine,
University of Lagos
University of Lagos Press
Contents
LIST OF FIGURES ........................................................................................................................ 3
LIST OF TABLES .......................................................................................................................... 4
Distinguished Ladies and Gentlemen ............................................................................................. 5
PREAMBLE ................................................................................................................................... 5
FOUNDING FATHERS OF EPIDEMIOLOGY AND THEIR CONTRIBUTIONS .................. 21
MODERN DAY EPIDEMIOLOGISTS AND WISDOM IN PUBLIC HEALTH ...................... 28
1
EPIDEMIOLOGY AND BIOSTATISTICS................................................................................. 34
MY CONTRIBUTIONS TO PUBLIC HEALTH ........................................................................ 45
CONTRIBUTION TO KNOWLEDGE ........................................................................................ 50
RECOMMENDATIONS .............................................................................................................. 64
ACKNOWLEDGEMENTS .......................................................................................................... 64
REFERENCES ............................................................................................................................. 69
2
LIST OF FIGURES
Figure 1: Illustration of the things that befall people ...................................................................... 8
Figure 2: An illustration of a Plague doctor.................................................................................. 9
Figure 3: A victim of bubonic plague ............................................................................................. 9
Figure 4: Illustration of bubonic plague patients .......................................................................... 10
Figure 5: Illustrations of Flagellant Brethren................................................................................ 11
Figure 6: Top 10 leading causes of death in the world, 2012. ...................................................... 13
Figure 7: Top ten causes of death in the world by percentage...................................................... 14
Figure 8: Sex-specific life expectancy at birth in Nigeria (1960-2013) ....................................... 16
Figure 9: Life expectancy at birth among men and women in selected countries, 2012 .............. 17
Figure 10: HIV prevalence among study groups, IBBSS Nigeria, 2010 ...................................... 17
Figure 11: HIV prevalence by State, Nigeria HIV sentinel survey, 2008 .................................... 18
Figure 12: HIV prevalence by State, Nigeria HIV sentinel survey, 2010 .................................... 19
Figure 13: Median HIV prevalence by country (2004 – 2005) .................................................... 19
Figure 14: Adult HIV Prevalence (15-49 years) 2014 by WHO region ....................................... 20
Figure 15: Hippocrates .................................................................................................................. 21
Fig. 16: John Graunt (1620-1674) ................................................................................................ 22
Figure 17: James Lind (1716-1794) .............................................................................................. 23
Figure 18: Dr William Faar........................................................................................................... 23
Figure 19: John Snow ................................................................................................................... 24
Figure 20: Ignaz Semmelweis ....................................................................................................... 25
Figure 21: Joseph Goldberger ....................................................................................................... 27
Figure 22: Top ten causes of deaths in Nigeria (2012) ................................................................ 30
Figure 23: Top ten causes of deaths in low-income countries in 2012 ......................................... 31
Figure 24: Top ten causes of death in high income countries....................................................... 31
Figure 25. Sample Medical News carried by the print media...................................................... 36
Figure 26: Selection of herbal bitters in Nigeria ........................................................................... 37
Figure 27: The Public Health Approach. ...................................................................................... 43
Figure 28: Pioneers of disease surveillance in Nigeria ................................................................. 46
Figure 29: Trend in HIV prevalence among Botswana pregnant women, 1992-2005 ................. 49
Figure 30: Knowledge score on HIV transmission modes by respondents' level of education .... 60
Figure 31: Age-specific patronage of female sex workers and current condom use rate by intracity bus drivers/attendants in Lagos .............................................................................................. 61
3
LIST OF TABLES
Table 1: Deaths from cholera by company supplying water to the household ............................. 25
Table 2: Leading causes of Deaths in the United States, 1990 and 2014 ..................................... 29
Table 3: Comparison of faecal coliform isolations during outbreaks and routine sampling ........ 51
Table 4: Proportionate Mortality Ratio (PMR) of Causes of Post-Neonatal Deaths, LUTH,
Lagos. May 1987-April 1988 ........................................................................................................ 52
Table 5: Significant risk factors for childhood diarrhoea in Iwaya Lagos ................................... 54
Table 6: association between child-feeding practices and the risk of prolonged diarrhoea in
children 6-36 months .................................................................................................................... 55
Table 7: Field assessment of the salt-sugar solutions prepared by mothers ................................. 56
Table 8: Distribution of sodium and glucose concentrations in SSS prepared by Nigerian mothers
....................................................................................................................................................... 57
Table 9: Prevalence of enteroparasites among hospital food handlers ......................................... 57
Table 10: Association between Asthma and Aeroallergens ......................................................... 59
Table 11: Knowledge of respondents on mother-to-child transmission of HIV ........................... 59
Table 12: Prevalence of influenza viruses in Nigeria ................................................................... 61
4
PROTOCOL
Mr Vice Chancellor, Sir,
Deputy Vice Chancellors
Provost, College of Medicine
Deans
Other Principal Officers of the University,
Academic and Non-Academic members of staff
My students: Old and New,
Family Members
Distinguished Guests
Gentlemen of the Press
My Christian brothers and sisters,
Distinguished Ladies and Gentlemen
PREAMBLE
Today is a great day. It is the day that the Lord has made and I will rejoice and be
glad in it. I was appointed a Professor about a decade ago by this great University,
the university of first choice and the nation’s pride. Since then, many of my
5
students and colleagues have been asking the question: When are you going to
deliver your inaugural lecture? My simple answer has been that, it will come at the
Lord’s appointed time.
Today is the appointed day and now is the Lord’s appointed time. My appointment
as a Professor was a blessing which immediately brought about many other
appointments and blessings. I had appointments with the World Health
Organization and the U.S. Centers for Disease Control and Prevention (CDC).
These contributed in some measure to the delayed delivery of this lecture. Mr VC
Sir, I am not trying to give excuses; just providing a little explanation, so that in
the end, you would temper justice with mercy.
This lecture is titled “Epidemiology: the beginning of wisdom in Public Health”.
To my knowledge, this is the first inaugural lecture to be given by a Professor of
Epidemiology in this great institution. Therefore, my main focus in this lecture will
be to explain what epidemiology is, who epidemiologists are, what epidemiologists
do and to show that epidemiologic principles and methods are prerequisites for
appropriate Public Health policies and interventions. Finally, I will share with you
some of my research endeavours, my modest contributions to Public Health
generally and to epidemiology manpower development in particular.
My Encounter with Epidemiology
Mr Vice Chancellor Sir, “Some are born great. Some achieve greatness and some
have greatness thrust upon them” (Shakespeare & Elam K, 2008). Some people are
born epidemiologists (Hippocrates and John Snow for example), some become
epidemiologists by chance while others become epidemiologists by choice. In my
own case, it was a combination of chance and choice. I came across Epidemiology
by chance and when I came across it, I began to sing “Oh pass me not, O blessed
Saviour” or should I say “Oh pass me not, O blessed discipline”.
In my final year as an undergraduate student, we were expected to write a termpaper on any subject of interest related to the biological and health sciences. At this
time, I was also working as an orderly at The Nebraska Methodist Hospital,
Omaha. Nebraska. During my years in this hospital, I encountered so many cases
of non-communicable disease conditions such as, emphysema, ischemic heart
disease, diabetes mellitus, stroke, etc. I did not come across a single case of
malaria, cholera, tuberculosis, or sickle cell anaemia. This observation prompted
me to choose a topic for that term-paper. “Disease patterns in developed and
developing countries”.
6
My interest was to examine and understand how diseases vary in frequency,
distribution and magnitude from country to country and from one region of the
world to another. I wrote to the World Health Organization requesting for data on
ischaemic heart disease, hypertension, diabetes and stroke. At this point, I knew
nothing about Epidemiology. When I eventually received the data, I was
disappointed that data on Nigeria and many other African countries were not
included. Secondly, I was amazed at the wide disparities in the incidence,
prevalence and mortality rates of these diseases between countries in which data
were available.
I told myself that this could not have happened by chance. There must have been
reasons behind the observed disparities. Following my graduation, I began to
search for postgraduate programmes which would enable me to explore in detail,
the determinants of diseases in human populations.
Mr Vice Chancellor Sir, ladies and gentlemen, this is where my journey began
when I enrolled for the MPH and subsequently the PhD programme in
Epidemiology at the University of Texas, Health Sciences Centre, School of Public
Health at Houston. Since then, I have never regretted pitching my tent in this area
of Public Health.
What is Epidemiology?
To many who are not in the medical field, epidemiology is not a familiar area of
specialty. Many think of epidemiology as the study of the skin; i.e. they tend to
confuse Epidemiology with Dermatology; some think it has to do with
immunization. Others have no idea. Even among many educated people, the
subject of epidemiology remains cloudy. So what is this subject called
Epidemiology? Sometimes I wonder, since so many have limited idea of the
subject (Epidemiology): Who do men think I am? This question is similar to what
our Lord Jesus asked his disciplines. In Luke 9:18 we read
“And it came to pass as he was alone with the disciplines: and he asked them:
Whom say the people that I am? They answering said; John the Baptist; but some
say, Elijah; and others say, that one of the old prophets is risen again. But he said
to them, But whom say you that I am? Peter answered and said, the Christ of God.
Jesus strictly warned them not to tell this to anyone.
Whereas Jesus strictly warned the disciplines not to tell anyone who He was, in my
own case I would strictly advise that you can tell anyone who epidemiologists are.
7
I will take a great deal of time to explain through history of epidemics and through
disease patterns in human populations what epidemiology is. The word
‘Epidemiology’ is derived from three Greek words: epi, meaning upon or on top
of, demos, meaning people, and logos, meaning the study of. Thus one can readily
combine these three words to surmise that epidemiology is a study of what befalls
the people. Those things that befall the people are illustrated in the figure below.
PHYSICAL
PEOPLE
BIOLOGICAL
SOCIAL
Figure 1: Illustration of the things that befall people
Of course, even with this, the definition may still remain unclear. Let me quickly
say that it is a study of those things that befall the people which can either make
them become sick or cause them to remain healthy. Technically, several definitions
of ‘Epidemiology’ have been used over the years. Some have become obsolete
because of the changing landscape of the field. I will talk about the technical
definitions later.
8
In the early development of the field, epidemiology was generally understood to
mean the branch of medical science which treats of epidemics. Webster’s New
World Dictionary defines epidemiology as the branch of medicine that investigates
the causes and control of epidemics (Guralnik, 1978). I will add that the epidemics
were mostly epidemics of infectious diseases such as cholera, plague, influenza,
smallpox, etc. For this reason, I will take a few minutes to remind us of the some
of the major pandemics that have plagued the world of mankind. I use the word
‘pandemics’ to refer to epidemics or outbreaks of an infectious disease spreading
through the human population across many regions of the world.
Some Major Pandemics in Human History:
Bubonic Plague: (The Black Death, 1347-1351 A.D.)
Mr Vice Chancellor Sir, there had been many pandemics of plague in human
history such as the Plague of Athens (430 BC), the Antonine Plague (165-180 AD)
the Justinian Plague (541 and 545 AD). The Black Death (Bubonic Plague) of
1347-1351 was the most famous and still remains one of the most deadly
pandemics in Earth’s history. It wiped out between 30-60% of Europe’s
population. It lowered the world’s population by 75-200 million people. This
disease killed millions and millions people within days. The disease arrived in
Western Europe through infected rats in merchant ships from Asia. Because of the
poor sanitary conditions of Europe in those days, the disease easily spread rapidly
from city to city creating widespread terror and panic.
Victims of the disease had certain swellings (buboes), either on the groin,
Figure 3: A victim of bubonic plague
9
Figure 2: An illustration of a Plague doctor
Figure 4: Illustration of bubonic plague
patients
under the armpits or the neck, which grew larger and larger even getting to the
size an apple, others to the size of an egg. Blood and pus seeped out of these
strange swellings. Four out of five victims died within days, and cities were
quickly overtaken by piles of rotting corpses, vast cemeteries and shallow mass
graves. In the city of Florence, one famous Italian writer, Giovanni Bocaccio put it
in this way: The victims ate lunch with their friends and ate dinner with their
ancestors in paradise (Dowling 2015).
What was the cause of the pandemic? Some thought it was caused by invisible
noxious particles in the air (miasma theory). This was why the plague doctors had
to wear long robes and special masks to cover their noses.1 The mask was filled
with aromatic herbs to keep away the bad smells, which was thought to be the
principal cause of the disease. The sweet smells were expected to protect them
from the disease.
Some blamed poisoned wells. Many unfairly blamed the Jews for killing Jesus and
bringing sin and death to the whole world. For this reason thousands and thousands
of Jews were persecuted in several countries of Europe. Some strongly believed
that the pandemic was as a result of the Wrath of God.
As a means of stopping the plague, a religious group, the Brethren of the Cross
popularly referred to as the Flagellant Brethren2 sprang up and grew in large
numbers. These were people who went around the entire continent of Europe in
groups of hundreds and thousands wearing long white robes marked front and back
with a red cross.
1
2
Source: https://en.wikipedia.org/wiki/Plague_doctor_costume
Source:Dowling (2015)
10
In an attempt to atone for people’s sins which resulted in the Black Death, these
people whipped themselves vigorously inflicting various degrees of injuries to
themselves in ritual public ceremonies.
Cholera pandemics:
There have been seven documented pandemics of cholera in history. The first six
pandemics were the most deadly, killing huge numbers of people in Asia, India,
Figure
5: Illustrations
Flagellant
Brethren
Europe,
Russia,of the
Americas,
the Middle East, Egypt and Africa. Victims died
within as little as 3 hours of the first symptoms mainly as a result of fluid loss from
acute diarrhoea, accompanied by vomiting, cramps and lowered blood pressure.
The cholera epidemic in Chicago in 1854 for example wiped out 5% of the city’s
population.
Mr Vice Chancellor sir, the cholera epidemic in London in 1854 cannot be
mentioned in passing, for it influenced the course of the discipline called
Epidemiology. So I will refer to it in greater detail later in this lecture. Suffice to
say, that it was an experience that forced many landlords and tenants to flee for
their dear lives after losing their friends and loved ones within hours. Within a
period of 10 days there were 500 fatal cases of cholera within a small
neighbourhood of Soho in London.
Spanish Influenza Pandemic (1918-1920)
During the height of World War I, a virulent strain of Influenza-A swept the world,
spreading quickly to regions as far apart as Asia, Australia, North America,
Europe, the Pacific islands and beyond. Whereas most influenza epidemics affect
11
weaker populations, such as infants or the elderly, this one involved a mutation that
allowed the virus to overtake the immune system and turn it against the victim’s
body. This resulted in a much higher mortality rate among the otherwise young
and healthy, whose immune systems were stronger, as well as a devastating toll on
social productivity. Everyday life stopped. Schools and shops closed, and even
gravediggers were too sick to bury the dead. In some cases, mass graves were dug
hurriedly and bodies were buried without coffins. This pandemic affected nearly
one third of the world’s population, causing between 50 million and 100 million
deaths. Mortality from the Spanish influenza was more than deaths from all the
wars of the 20th century combined!
Decline in Pandemics:
Mr Vice Chancellor, today we are living in an age full of divine blessings although
mankind has abused these blessings in many ways. In the book of Daniel 12: 4 we
read,
But thou, O Daniel, shut up the words, and seal the book, even to the time of the
end: many shall run to and fro, and knowledge shall be increased.
Since the turn of the 19th century, we have been living in era of great increase in
knowledge, resulting in so many discoveries, inventions and general technological
and scientific advances as foretold in the Bible. With the discovery of vaccines by
Edward Jenner and antibiotics by Alexander Fleming, coupled with general
improvements in water and sanitation, we are not experiencing mass outbreaks of
diseases in the same frequency and magnitude as was the case centuries ago. This
is not to say that we should quickly forget the HIV/AIDS pandemic, the Avian
Influenza (Bird Flu) and the Swine flu, the Ebola Viral Disease and the Lassa fever
epidemics. These can never be compared with the Black Death or the Spanish
Influenza pandemics.
In the last 100 years or so however, non-communicable diseases have become very
prominent, not only in developed countries but also in the developing ones (Figure
6Figure 6: Top 10 leading causes of death in the world, 2012.). Currently, ischaemic
heart disease is the leading cause of death killing 7.4 million people with a
proportionate morbidity ratio of 13.2%.
12
Figure 6: Top 10 leading causes of death in the world, 2012.
13
Figure 7: Top ten causes of death in the world by percentage
Because of the difficulty in defining epidemics of chronic non-communicable
diseases, various definitions of epidemiology have been proposed. I will use the
one that is widely used and can be found in the dictionary of epidemiology.
Epidemiology is the study of the distribution and determinants of health-related
states or events in specified populations, and the application of this study to the
control of health problems (Last, 2001).
There will be no examination after this lecture. So, if I say anything that seems not
to be clear, do not worry; just smile. Let me break the definition down so that you
will agree with me that ‘Epidemiology’ is the beginning of wisdom in Public
Health.
14
Distribution in the definition implies that epidemiologists are interested in
describing how diseases are distributed in the population by different
characteristics of PERSONS such as age, sex, occupation, level of education,
social habits, etc), PLACE and TIME.
Disease by PERSON (Gender)
I will just use a few examples to make the point clear. Consider sex as a
characteristic, we observe that generally women report more illnesses than men
both in the hospitals and in the community. But throughout life, the risk of death is
higher in men than in women, and we have more widows than widowers.
Mr Vice Chancellor Sir, let me point out that although our women carry a heavy
morbidity burden, men are also disadvantaged in many ways as far as health is
concerned. Nobody seems to be interested in them either. We have specialists in
Maternal and Child Health. I do not know of any specialist in Paternal Health.
Right from birth girls have a biological advantage over boys. Neonatal mortality is
particularly higher for boys than girls during the first month of life. The biological
advantage of women continues through all life stages. Even with genderinequalities in traditional societies like Nigeria, women continue to live longer than
men. This pattern has been consistent over several years (Figure 3). In countries
with low maternal mortality ratios and greater gender equality, the difference in
life expectancy is even wider (Figure 4), the difference being on the average, about
5 years.
We also know that the prevalence of hypertension is higher in men than in women
across all ethnic and racial groups.
15
Fig. 3. Sex-specific Life expectancy at birth in
Nigeria, 1960-2013
70
65
60
55
50
45
40
35
30
25
20
Males
Females
1960"
1970"
1980"
1990"
2000"
2010"
Figure 8: Sex-specific life expectancy at birth in Nigeria (1960-2013)
16
2013"
90
80
70
60
50
40
30
20
10
0
Males
Females
Figure 9: Life expectancy at birth among men and women in selected countries, 20123
Disease by PERSON (Social Habits):
When considering sexual behaviour, we observe that HIV prevalence shows
remarkably different patterns among different subgroups of the population.
27.4
30
21.1
25
17.2
20
15
10
5
2.4
2.5
2.6
4.2
4.1
0
Figure 10: HIV prevalence among study groups, IBBSS Nigeria, 20104
The prevalence of HIV among female sex workers (formerly known as prostitutes,
later modified to commercial sex workers, then female sex workers and who may
3
Data Source: http://www.who.int/mediacentre/news/releases/2014/world-health-statistics-2014/en/
4
*Source: FMOH HIV Integrated Biological and Behavioural Surveillance Survey, 2010
17
subsequently be addressed as female hospitality professionals) is about 6 times
higher than women in the general population. HIV prevalence among men having
sex with men (MSM) is about 4 times higher than men in the general population.
Disease by PLACE
We have observed over the years that there is consistent disparity in HIV
prevalence in Nigeria by state. While Benue State has a singular honour of
consistently occupying the number one position (highest prevalence), Akwa Ibom
State has delightfully competed with other states to occupy the number two
position.
Figure 11: HIV prevalence by State, Nigeria HIV sentinel survey, 2008
The South-western and the North-western Zones have shown lower HIV
prevalence rates than most other Zones.
18
Figure 12: HIV prevalence by State, Nigeria HIV sentinel survey, 2010
When examining HIV prevalence by country, we observed that there is
considerable disparity between countries. In sub-Saharan Africa, Botswana,
Swaziland and South Africa have the highest HIV prevalence of about 30%, i.e.
about 1 in 3 adults whereas in Niger and Ghana, the prevalence is between 2 and
3% respectively.
Figure 13: Median HIV prevalence by country (2004 – 2005)
Besides variation in HIV prevalence between countries, there is consideration
variation between regions of the world. Sub-Saharan Africa has the highest
19
prevalence of HIV and carries 70% of the HIV/AIDS global burden with nearly 1
in every 20 adults (4.8%) living with HIV.
Figure 14: Adult HIV Prevalence (15-49 years) 2014 by WHO region5
Disease by TIME:
With respective to TIME, generally there are more deaths during the winter than in
the summer months of year in temperate regions of the world. In Nigeria, one does
not need to be an epidemiologist to observe that we have excess mortality from
road traffic accidents during Christmas and Easter periods than other periods of the
year. There is higher risk of death in December/January compared to other periods.
Epidemics of cerebro-spinal meningitis usually occur in meningitis belt during dry
season when weather conditions are harsh with dusty winds and high temperature.
With respect to secular trend, in the last 50 years, the incidence of stroke and
cancers has been increasing even in developing countries.
5
Source:http://www.who.int/gho/hiv/hiv_013.jpg?ua=1
20
Determinants (in the definition) involve the understanding of how and why
diseases occur and why they vary in frequency. This aspect is concerned with
determining the causes and uncovering risk factors for diseases. We may ask, why
do women live longer than men? Why is HIV prevalence higher in Benue State
than others? Why do female sex workers have the highest HIV prevalence? Why is
there more deaths and accidents during Christmas and new year compared to other
periods? Why is incidence of stroke increasing?
Part of the sex differences in mortality can be explained by the fact that men are
more likely to be engaged in risky occupations, they engage in risky behaviour
such as use of alcohol and smoking as well as socially and culturally determined
aggressive roles and behaviours which expose them to injuries. Additionally, it is
very probable that there are some genetic, hormonal or immune system
mechanisms that make females less likely to die than males.
The use of the phrase health-related states implies that epidemiologists are not
only merely concerned with what makes people sick, they are concerned with a
broad spectrum of illness (Discomfort, Dissatisfaction, Disease, Disability, Death)
to a broad of spectrum of wellness; including physiological states, immunological
states, injuries, accidents, etc. The whole essence of epidemiology is to understand
risk factors for diseases and to use this knowledge for disease prevention and
control. Thus Epidemiology is the beginning of wisdom in Public Health.
FOUNDING FATHERS OF EPIDEMIOLOGY AND THEIR
CONTRIBUTIONS
Let me at this point to take a little journey through time to share with you the
genealogy of epidemiology. This little journey may help to drive home the point
concerning what epidemiology is and to further affirm that Epidemiology is the
beginning of wisdom in Public Health.
Mr Vice Chancellor Sir, time and space will not allow me to enunciate the
numerous and far-reaching contributions of the founding fathers of epidemiology
to disease prevention and control in Public Health. I will however mention just a
few:
Hippocrates: (460 – 370 BC)6
The history of Epidemiology dates back to about 460 BC
when Hippocrates, generally considered the father of modern
6
Source:www.gettyimages.com/photos/hippocrates
21
Figure 15: Hippocrates
Medicine wrote in his treaties on Airs, Waters and Places. Quote:
Whoever wishes to investigate medicine properly should proceed thus; in the first
place to consider the seasons of the year, and what effects each of them produces
(for they are not all alike, but differ much from themselves in regard to their
changes). Then the winds, the hot and the cold, especially such as are common to
all countries, and then such as are peculiar to each locality. He must also consider
the qualities of the waters, for as they differ from one another in taste and weight,
so also do they differ much in their qualities.
In the same manner, when one comes into a city to which he is stranger, he ought
to consider its situation, how it lies as to the winds and the rising of the sun; for its
influence is not the same whether it lies to the north or the south, to the rising or to
the setting sun. These things one ought to consider most attentively, and
concerning the water which the inhabitants use, whether they be marshy and soft,
or hard, and running from elevated and rocky situations, and then if saltish and
unfit for cooking, and the ground, whether it be naked and deficient in water, or
wooded and well watered, and whether it lies in a hollow, confined situation, or is
elevated and cold, and the mode in which the inhabitants live and what are their
pursuits, whether they are fond of drinking and eating to excess, and given to
indolence, or are fond of exercise and labour, and not given to excess in eating and
drinking” (Roht, et al.,1982).
The summary of this treatise is that the development of disease might be
influenced by the physical environment, the social habits of the individual as well
as seasonal factors. He noted that diseases like malaria and yellow fever were more
likely to occur in swampy areas. It was not known at the time that mosquitoes were
responsible for these diseases until 1900 when Walter Reed, a United States
physician working in the tropics made the connection. Hippocrates was the first
person to use the terms “epidemic” and “endemic”.
Following this landmark treatise, nearly 2000 years elapsed before such causes as
suggested by Hippocrates were considered. There was limited effort to measure
their impacts on health and disease.
John Graunt ( 1620-1674)
In 1662, John Graunt7 wrote a book on “Nature and
Political Observations Made Upon the Bills of
Mortality”. A prosperous haberdasher until his
business was destroyed in the Great Fire on London in
1666, he began to study the death records of parishes
7
Source: http:alchetron.com/John Graunt 1071708-W
Fig. 16: John Graunt (16201674)
22
and noticed that certain phenomena of death statistics were commoner than others.
This was the first attempt to employ quantitative methods to measure disease and
deaths in a population. John Graunt noted that there was excess mortality in men
compared to women. He also noted seasonal variations in mortality as suggested
by Hippocrates.
James Lind (1716-1794)
James Lind was a Scottish doctor who
worked with the British Navy. During his
days, thousands of sailors died of the disease
scurvy particularly during long voyages in
which there was shortage of fruits and
vegetables. In one of the trips, 1400 sailors
died out of 1900 (a mortality rate of 74%).
James Lind conducted the first clinical trial
in the history of Medicine by assigning the
12 sailors who had scurvy to 6 six treatment
groups. The groups all had the same diet but
Figure 17: James Lind (1716-1794)
in each group there were slight
modifications. One of the groups was given
two oranges and two lemons daily. He
observed that by the fifth day, the group that was given oranges and lemons had
recovered and were fully fit to return to work. He concluded that scurvy was a
disease resulting from dietary deficiency particularly citrus fruits.
Wisdom: James Lind recommended that citrus fruits be introduced as a regular
part of the sailors’ diet. By this time, nothing was known about vitamin C. With
the work of James Lind, the incidence of scurvy was greatly reduced among
British sailors. This is why British sailors are comically called “limeys”.
William Faar: (1807-1883)
William Faar was a British physician, who was given the
responsibility for collecting and compiling official vital
statistics for England and Wales. He was able to show
patterns of morbidity and mortality among occupational
groups. He initiated the classification of diseases. He is
considered the originator of today’s vital statistics. This
practice of birth and death registries, which were
established in Europe during the 18th and 19th centuries
and in the United States in the 20th century, gave health
officials a means of identifying risk factors for
Figure 18: Dr William Faar
23
maternal and infant mortality. Public health measures were then designed to reduce
these factors. For example, in the United States, the practice of providing milk to
nursing mothers was established when a relationship was found between infant
mortality and nutrition.
John Snow (1813-1858)
For many students of Epidemiology the
name of William Farr is not as popular as
that of John Snow.8 John Snow popularly
referred to as the father of Epidemiology,
is not often remembered for his work on
anaesthesia, being the first doctor to
administer chloroform to Queen Victoria
(during the delivery of her 8th child, Prince
Leopold), but for his pioneering
epidemiological investigation on the cause
and mode of transmission of cholera.
There were two notable outbreaks of
cholera in London in the 19th century. The
first one was in 1849. This was followed
by another devastating outbreak in 185354. Within a period of 10 days, there were
over 500 deaths from cholera in a small
neighbourhood of Soho in London. John
Figure 19: John Snow
Snow used the list of deaths from cholera
and prepared a spot map. From the spot map he noted that nearly all the deaths
occurred within a short distance of one of the pumps, the Broad street pump. There
were just 10 deaths in houses located near other street pumps. He concluded that
cholera was associated with consumption of water from the Broad Street Pump and
consequently requested that the handle of the pump be removed.
To further test his hypothesis, he identified the homes of each person who died
from cholera epidemics in London 1848-49 and 1853-54. He compared deaths
from cholera in homes with different water supplies (Table 1). On the basis of
these comparisons, John Snow was able to show that cholera mortality varied
according to source of water supply.
8
Source: https://en.wikipedia.org/wiki/John_Snow
24
Table 1: Deaths from cholera by company supplying water to the household
Water Company
Southwark & Vauxhall
Lambeth Company
Rest of London
No. of Houses
40,046
26,107
256,423
Cholera
deaths
1263
98
1423
Cholera deaths per
10,000
315
37
59
Wisdom: Removal of handle of the Broad street pump which led to decline of the
epidemic. Improvements in water supply with attendant decline in cholera
incidence. Snow’s findings inspired fundamental changes in water and waste
systems in London and which led to similar changes in other cities and a
significant improvement in general public health around the world.
Ignaz Semmelweis (1818-1865)9
Ignaz Semmelweis was a Hungarian medical
doctor who specialized in Obstetrics. He
worked at Vienna General Hospital in 1847.
There he observed that women delivered by
physicians and medical students had a much
higher post-delivery mortality rate than
women delivered by midwives. In fact in the
first month that he worked in Maternity Ward
No 1, the mortality rate was 17% fatality rate
whereas in Ward 2 the mortality was 2%. The
mortality difference was so clear that
pregnant women in the city women would
rather give birth in the streets around the
hospital than be admitted to Ward No 1.
Figure 20: Ignaz Semmelweis
Semmelweis concluded that the higher rates
of childbed fever in women delivered by physicians and medical students was
associated with the handling of corpses during autopsies (and failure to wash
hands) before attending to the pregnant women.
Wisdom: He introduced mandatory handwashing policy for physicians and medical
students and the mortality from childbed fever was greatly reduced. His findings
were published in 1850, but his work was ill received by his colleagues, who
discontinued the procedure. Disinfection did not become widely practised until
9
Source: https://en.wikipedia.org/wiki/Ignaz_Semmelweis
25
British surgeon Joseph Lister discovered antiseptics in 1865 in light of the work of
Louis Pasteur.
26
Joseph Goldberger (1874-1929)10
Another prominent pioneer of Epidemiology
who is often not much celebrated is Joseph
Goldberger. Joseph Goldberger was an
American physician and epidemiologist who
worked with United States Public Health
Service. During his time, the disease pellagra
was endemic in the Southern part of the United
States. It was believed that pellagra was an
infectious disease caused by spoiled corn
(maize). Using experimental and observational
epidemiologic
approach,
Goldberger
determined that pellagra was associated with
Figure 21: Joseph Goldberger
poor dietary intake. This was long before
vitamins were isolated.
Wisdom: Goldberger suggested that diet should be supplemented with meat, eggs
and milk in areas where pellagra was prevalent. This greatly reduced the incidence
of the disease.
10
Source: https://en.wikipedia.org/wiki/Joseph_Goldberger
27
MODERN DAY EPIDEMIOLOGISTS AND WISDOM IN PUBLIC
HEALTH
Richard Doll and Austin Bradford-Hill
Richard Doll was not the first person to come up with the idea that cigarette
smoking might be associated with the development of cancer of the lung. But
according to Francis Galton, “In science credit goes to the man who convinces the
world, not the man to whom the idea first occurs” (Riedle, 2005). The first
comprehensive study on the association between smoking as a causal factor in the
aetiology of carcinoma of the lung was done by Sir Richard Doll and AustinBradford-Hill (Doll and Hill, 1950). They used a case-control approach (709 cases
and 709 controls) to investigate and test their hypothesis. They were able to
establish that there was a consistent and statistically significant association
between the number of cigarettes smoked and the risk of carcinoma of the lung.
They stated in their report “the risk of developing the disease increases in simple
proportion with the amount smoked, and that it may be approximately 50 times as
great among those who smoke 25 or more cigarettes a day as among nonsmokers”.
Following the results of this classic case-control study, they also embarked upon a
retrospective cohort study of 34,439 physicians. Physicians were classified into
three categories: current smokers, ex-smokers and non-smokers. Mortality from
various causes was evaluated. The study showed that on the average smokers die
10 years younger than their non-smoking counterparts. It also showed that those
who stopped smoking at age 50 reduced their risk of death by half while those who
stopped at 30 avoided the smoking-associated risk of mortality. These studies were
subsequently confirmed by studies from various countries.
Wisdom: Cigarette commercials were banned from British television in 1965 and
from radio in 1975. Billboards and newspapers were prohibited from advertising
cigarettes as from 2003.
The Framingham Heart Study:
This is a prospective epidemiologic cohort study that enrolled over 5000 residents
in a community of Framingham, Massachusetts, U.S.A. The study has been
following these individuals since 1948 till date. Over the years, the Framingham
Study population has led to the identification of the major cardio-vascular disease
(CVD) risk factors - high blood pressure, smoking, obesity, diabetes, and physical
inactivity, High Density Lipoprotein (HDL) cholesterol levels, age, etc. The
importance of the major CVD risk factors identified in this group have been shown
in other studies to apply almost universally among other racial and ethnic groups.
28
Wisdom: Knowledge of these risk factors has led to the development of effective
management and preventive strategies for cardiovascular disease.
Epidemiologic Transition (Morbidity and Mortality Patterns):
From the historical context, it would appear that epidemiology is largely about
investigating outbreaks of acute communicable diseases. This was actually true
during the 18th and 19th centuries; but there is much more to epidemiology than
investigation of infectious disease outbreaks. In many developed countries there
has been a clear shift in the disease patterns of morbidity and mortality. The pattern
has moved from one of high mortality from epidemics of infectious diseases and
famine, to one of degenerative and man-made diseases (such as those attributed to
life-style and environment). In this regard Oman (1974) has proposed that three
major epidemiologic stages be recognized and aligned with demographic
transitions.
1) The Age of Pestilence and Famine; when mortality is high and fluctuating,
thus precluding sustained population growth. In this stage the average life
expectancy at birth is low, between 20 and 40 years.
2) The Age of Receding Pandemics when mortality declines progressively; and
the rate of decline accelerates as epidemics become less frequent or
disappear. The average life expectancy at birth increases steadily from about
30 to about 50 years. Population growth is sustained and begins to assume
an exponential phase.
3) The Age of Degenerative and Man-Made Diseases: when mortality
continues to decline and eventually approaches stability at a relatively low
level. The average life expectancy at birth rises gradually until it exceeds 50
years. It is during this stage that fertility becomes the crucial factor in
population growth.
These stages can be clearly observed in developed countries of North America and
Western Europe. In the United States mortality from all causes has declined by
54% between 1990 and 2010 (Tippet, 2014). Table below shows that whereas
Infectious Diseases were the leading causes of death in the 1900, noncommunicable diseases are more prominent currently (Table 2).
Table 2: Leading causes of Deaths in the United States, 1990 and 2014
1900
Causes of Death
2014
Ranks (Deaths per
100,000)
29
Causes of Death
Ranks & PMR (%)
Pneumonia & Influenza
Tuberculosis
Gastrointestinal Infections
Heart Diseases
Cerebrovascular Disease
Nephropathies
Accidents
Cancers
Senility
Diphtheria
1 (202.2)
2 (194.4)
3 (142.7)
4 (137.4)
5 (106.9)
6 (88.6)
7 (72.3)
8 (64.0)
9 (50.2)
10 (40.3)
Diseases of the Heart
Cancers
COPD
Unintentional Injuries
Cerebrovascular Disease
Alzheimer’s Disease
Diabetes Mellitus
Influenza & Pneumonia
Nephropathies
Suicide
1 (23.4)
2 (22.5)
3 (5.6)
4 (5.2)
5 (5.1)
6 (3.6)
7 (2.9)
8 (2.1)
9 (1.8)
10 (1.6)
Such dramatic transition has however been delayed in many developing countries
as they are still confronted with poverty, poor sanitation, gross mismanagement of
resources and widening inequalities in access to care; in addition to the universal
adoption of western lifestyles and unfriendly physical and social environments. In
Nigeria for example, infectious diseases are still the leading causes of morbidity
and mortality; while non-communicable diseases, are also emerging. Stroke and
ischaemic heart disease, for example, rank among the top 10 killers in Nigeria.11
13.9
Lower respiratory infections
10.4
HIV/AIDS
8.7
Malaria
6.3
Diarrhoeal diseases
5.0
Pre-term birth complications
4.3
Birth asphyxia
3.6
Meningitis
3.4
Stroke
2.6
Ischaemic heart disease
2.0
Protein-energy malnutrition
0.0
2.0
4.0
6.0
8.0
10.0
Proportionate mortality rate
Figure 22: Top ten causes of deaths in Nigeria (2012)
11
Source: WHO. Nigeria: WHO Statistical Profile. http://www.who.int/gho/countries/nga.pdf
30
12.0
14.0
91
Lower respiratory infections
65
HIV/AIDS
53
Diarrhoeal diseases
52
Stroke
39
Ischaemic heart disease
35
Malaria
33
Pre-term birth complications
31
Tuberculosis
29
Birth asphyxia
27
Protein-energy malnutrition
0
10
20
30
40
50
60
70
80
90
100
Deaths per 100,000 population
Figure 23: Top ten causes of deaths in low-income countries in 2012
Ischaemic heart disease
Stroke
Trachea/Bronchus/Lung cancers
Alzheimers disease
Lower respiratory infections
COPD
Colon/Rectum cancers
Hypertensive heart disease
Diabetes mellitus
Breast cancer
0
20
40
60
Figure 24: Top ten causes of death in high income countries
31
80
100
120
140
160
Paradigm Shifts in Epidemiology
In terms of methodologic approach and depth of inquiry, three stages
epidemiologic transition have been proposed by Melvyn Susser (Susser, 1996).
They are the era of sanitary statistics with its paradigm (miasma), (2) the era of
infectious diseases with its paradigm, the germ theory of diseases and (3) the era
of chronic diseases with its paradigm the “black box”. The name “black box” as
proposed by Susser is to indicate an era in which epidemiologists related exposure
to an outcome without any obligation to interpolate or understand any intervening
factors or pathogenesis.
Exposure
Black box
Disease
The work of British epidemiologists Richard Doll and Austin Bradford Hill
(mentioned earlier) on the association between smoking and lung cancer was a
classic case. Today, epidemiology has expanded and is also adopting the Chinese
boxes paradigm, a paradigm that emphasizes a multilevel understanding of
exposure-disease relationship: including the molecular, environmental, societal and
microbiological interactions and processes. This conceptual approach of combining
molecular, societal and population-based aspects to study health-related problems
is now popularly referred to as eco–epidemiology. Epidemiologists are currently
thinking outside the “black box”, while also thinking about what goes on inside the
“black box”. Epidemiologic studies are now carried out to investigate “disease
susceptibility genes” “interaction between genes and environment” as well as
“gene-gene” interactions.
32
• genetic
• environmental
• societal
Exposure
Black box
• microbiological
• molecular
• epigenetic
processes
• environmental
• social
• political
• financial
Disease
It is well known that specific susceptibilities to some diseases may be inherited.
Some individuals may be predisposed to certain illnesses because of certain genes
inherited from their parents. For example a large percentage of individuals with
breast and ovarian cancers have inherited susceptibility for these diseases. Other
forms of cancer are known to run in families and are due to hereditary influences.
The Chinese boxes paradigm has given birth to molecular epidemiology, a branch
of epidemiology and medical science that focuses on the contribution of genetic
and environmental risk factors, identified at the molecular level, to the aetiology,
distribution and prevention of disease within families and across populations. The
increased attention to the mechanism of action has perhaps forced epidemiologists
to include “processes” as part of the latest definition of epidemiology (Porta et al.,
2014).
33
EPIDEMIOLOGY AND BIOSTATISTICS
Mr Vice Chancellor Sir, when I informed my colleagues about my inaugural
lecture, the one thing that many of them feared was that they were going to be
bombarded with a load of statistical jargon and equations. This is so, because in the
College, all postgraduate students take the course in Medical Statistics and I am
more often remembered for my lectures in Biostatistics than for those in
Epidemiology. I do not know why. But it could be that, to some of the students
“the fear of medical statistics is the beginning of wisdom”. But I have decided that
since this lecture is coming up in the afternoon, and the audience is a mixture of
gown and town, I would not bore anyone with statistical jargon and equations.
Mr Vice Chancellor Sir, ladies and gentlemen, the relationship between
Biostatistics and Epidemiology is like that of husband and wife. In this lecture, I
will not go into the argument as to which one is the husband or which is the wife.
That argument is a topic for another day. A husband alone cannot be a complete
parent, neither can the wife alone. A child needs both parents for proper social and
psychological development. Many of the problems we have in Lagos and other
societies is that we are breeding children without the full complement of
parenthood. It is even becoming an acceptable norm to deliberately have children
without fathers as well as children without mothers.
For Epidemiology to manifest its full potential and serve as the beginning of
wisdom in Public Health, it must partner with Biostatistics. This is why many
renowned Epidemiologists have formal training in biostatistics and many
Biostatisticians have formal training in Epidemiology. This is why I pursued a
formal training in Statistical Methods following my doctoral degree in
Epidemiology. To say ”I like Epidemiology but not Biostatistics” is like a Yoruba
saying “I like amala, but not ewedu” or like an Akwa Ibomite saying “ I like afang
soup but not foofoo” or like an American saying “I like mashed potatoes but not
gravy”.
Advancement in epidemiology demanded emphasis on the scientific method,
quantification, measurement, and hypothesis testing. Epidemiology and
Biostatistics are the basic sciences of Public Health aiming at telling the truth about
potential risk factors and disease. It also aims at telling the truth about the benefits
of public health interventions, medical procedures, drugs, etc. In telling the truth,
exposures/susceptibilities and outcomes must first be measured in a quantitative
manner. Statistical principles and methods are applied at every level of
epidemiologic endeavour ranging from identification and quantification of health
problems of populations as well as in the design, conduct, analysis and
interpretation of epidemiologic research.
34
In measuring the occurrence of a disease or a health event, one must first of all
define a “case”. It would appear to a layman that definition of case is a simple
matter. Among two clinicians evaluating the same patient, disagreement may arise
as to whether the patient is presenting with one form of disease or the other. In
going out in the community to investigate an outbreak of Lassa fever, it may be
difficult to determine whether a febrile person is a case of Lassa fever. Because the
symptoms of Lassa fever are so varied and non-specific, even clinical diagnosis is
often difficult, especially early in the course of the disease. Therefore placing
individuals into any of the various disease categories has often been based on a
clustering of signs and symptoms, as well as a range of biochemical values and/or
a history of exposure. The final classification will be established by procedures
employing implicit statistical methods and clinical and epidemiological reasoning.
Once individuals are classified, then epidemiologic measures begin. Then rates of
occurrence of diseases and other health events are computed. These measures are
called “measures of disease frequency.” Once measured, the association between
exposures and outcomes are then evaluated by calculating “measures of association
or effect.” Finally, the impact of removal or modification of an
exposure/susceptibility on the outcome is evaluated by computing “measures of
potential impact.” In general, measures of disease frequency are needed to generate
measures of association, and both these are needed to get measures of impact.
Measures of Disease Frequency
Simple Counts: Simple counts refer to the number of persons with the particular
disease condition. For example; the number of cases of tuberculosis in a state or
Local Government. Simple counts may be useful for public health officials for the
purpose of allocating resources, but are not useful for making statements on the
risk or odds of another person contracting the disease. Mere counts can be
misleading because information on the size of the population from which the cases
came from has not been taken into account. In order to take this into consideration,
the epidemiologist usually measures the frequency of a disease by either incidence
or prevalence. While incidence refers to the rate of occurrence of new cases in a
population over a specified period of time, prevalence on the other hand refers to
the proportion of the population affected by a disease condition at a given point in
time (point prevalence) or at a given to period (period prevalence). Consequently,
prevalence considers those who have survived the condition and those in which
recovery is delayed; while incidence measures the rate or speed at which new cases
enter into a population.
35
The Process of Establishing Causation in Epidemiologic Studies
Mr Vice Chancellor Sir, I have been warned to stop drinking Ijebu garri because it
is believed to be associated with impaired vision. I have also been warned that I
should avoid okra soup as it is believed the associated with weak penile erection.
There is also the controversy in the literature whether oral contraceptives are
causally associated with development of breast cancer. Recently in the United
States, a judgement was delivered in favour of an Alabama woman Jacqueline
Salter Fox, who died of ovarian cancer (Wernick, 2016). The claim was that the
ovarian cancer resulted from her prolonged use of Johnson and Johnson powder.
For this case, the court awarded her a compensation of 72 million US dollars. More
recently, another woman in St Louis was awarded a $55 million compensation for
a similar claim.
The cartoon (Figure 25) summarizes an example of a number exposure factors and
supposed diseases/benefits. These are familiar examples of some of the things we
hear in the news or read in health magazines.
Figure 25. Sample Medical News carried by the print media
Apart from the risks of disease resulting from specific exposures, there are many
claims of cure from herbalists, trado-medical, and even orthodox medical
practitioners for various ailments. During the outbreak Ebola Viral Disease in
36
Nigeria, bitter kola was very scarce and when found, it was expensive because it
was claimed to be a cure for the disease. Today, in Nigeria there has been an
epidemic of “bitters” claiming to cure all sorts of illnesses. We have Swedish
bitters, Yoyo Bitters, Alomo Bitters and Dr Iguedo Bitters, Oko Oloyun (the
pregnant woman's spouse), Koboko bitters, Osomo, Epa Ijebu, Galant bitters and
the Gbogbonise bitters (cure all, heal all).
Figure 26: Selection of herbal bitters in Nigeria12
These are just a few examples of associations between exposures and health
benefits. Epidemiologists are the professionals who are trained to provide answers
to such claims as they affect populations. How do epidemiologists establish that a
given exposure is associated with a particular outcome? Or that a given treatment
improves an outcome. Let me emphasise that epidemiologists do not establish a
cause-and-effect relationship on an individual level but for population subgroups.
Almost all observations in medicine and public health, whether physiological,
biochemical, immunological or social; exhibit considerable variations from person
to person making it difficult to establish the effect of a given factor or intervention
on an individual. Although cervical cancer is associated with multiple sexual
partners, there are women with many sexual partners who do not develop the
disease. Although cigarette smoking is associated with lung cancer, it is possible to
find an individual who has smoked for years without developing the disease, and
paradoxically one who never smoked developing cancer of the lungs.
12
Source: http://www.authorityngr.com/2015/11/Checking-unbridled-influx-of-bitters-drink-in-Nigerian-market/
37
Epidemiologists therefore use a probabilistic (statistical) approach in establishing
causation and then make statements about groups of individuals with a given
exposure or characteristic.
Measures of Association
Epidemiologists commonly express the likelihood of developing a disease in a
group of individuals with an exposure, or characteristic (Ie) as a ratio of the
likelihood among those without the exposure (Io); and refer to this quotient, (Ie / Io)
as the relative risk (RR). Because the relative risk of developing lung cancer is
about 4 to17 times among smokers compared to non-smokers, epidemiologists may
use this is a preliminary basis for suggesting that smoking may be causally
associated with cancer of the lung and thus recommend that individuals refrain
from smoking. A risk ratio of 3 would imply that individuals with the exposure
characteristic are three times more likely to develop the disease compared to those
without. If the exposure is beneficial such as in exposure to vaccines, drugs, or
other useful interventions, then incidence in the exposed group should be expected
to be lower than the incidence in the unexposed, thus the relative risk should be
less than 1.
For diseases or outcomes which may take several years to manifest,
epidemiologists often rely on the case-control approach which compares
individuals who already have the disease with those who do not. Because of the
nature of the data in case-control studies, the risk of the disease, however, cannot
be determined. Epidemiologists usually compute the odds of exposure among the
‘case’ group as well as for the ‘control’ group. The quotient of the two odds is the
odds ratio (OR), which is mathematically equivalent to the relative risk if the cases
and controls were representative of their respective populations and the frequency
of the disease in the population is low. The hazard ratio (HR), frequently used in
survival studies and clinical trials, measures the instantaneous risk between two
groups at any given point in time.
Measures of Impact
As a measure of impact epidemiologists compute the attributable risk (AR) or
excess risk (Ie - Io). The attributable risk measures the absolute difference in risk,
i.e. the excess risk that can be ascribed to the exposure variable among the exposed
group. The attributable risk percent (Ie-Io)/Ie *100 equivalent to (RR-1)/RR*100 is
a measure of the percentage of the risk of a disease that can be ascribed to
exposure among those individuals with the exposure while the population
attributable risk percent; [(AR)Pe ] or [Pe(RR-1)/ Pe (RR-1)+1*100] percent
provides information of the extent to which the disease can be reduced in the entire
38
population if the given factor is completely removed (Pe is the proportion of the
population with the exposure characteristic).
If the exposure is protective, different terminologies are used to describe the extent
of protection that can be ascribed to the factor, thus instead of attributable risk
(AR) we compute the absolute risk reduction (ARR) which is Io – I e as well as
the relative risk reduction (RRR) (also referred to as the “prevented fraction”) as
(I o – I e) * 100 = ARR * 100. In vaccine trials, this measure is known as vaccine
efficacy. This measure provides information as to the degree of protection that can
be attributable to the vaccine. Furthermore, epidemiologists then compute the NNT
(number needed to treat), which is the reciprocal of the ARR. The NNT measures
how many people need to be treated in order for one to benefit from the treatment.
39
Internal validity in Epidemiologic Investigations
Chance
When a risk or an odds ratio is determined, or when a difference in a quantitative
measure between population subgroups is observed, it is still necessary to enquire
whether such an association or difference could have arisen by chance. This is
often done by performing statistical tests of significance such as the t-test, the chisquare test, the F-test, etc. A measure which is often reported is the p-value. The pvalue tells us the probability that an effect at least as extreme as the one observed
in a particular study could have occurred by chance alone, suggesting therefore,
that there is truly no relationship between the exposure and the disease. By
convention, a p-value of 0.05 or less is considered statistically significant. A more
informative measure than the p-value is the confidence interval, which provides a
range within which the true magnitude of the effect or difference lies.
Bias
Epidemiologists in search for the truth must ensure that an association between an
exposure and disease is not as a result of systematic error (bias) arising either in the
process of selecting the subjects for a study or in the way information is collected
and interpreted for the different groups.
Confounders
A statistically significant association between exposure and effect, devoid of bias,
does not in any way mean that the association is valid. Epidemiologists, in their
quest for the truth must evaluate whether the association could have been
contributed by other variables called confounding factors. Confounding involves
the possibility that an observed association is due, totally or in part, to the effects
of another variable or variables (other than the exposure under investigation) that
could affect their risk of developing the outcome being studied. Confounding
occurs when the effects of two associated exposures have not been separated,
resulting in the interpretation that the effect is due to one variable rather than the
other. The consequence of confounding is that the estimated association is not the
same as the true effect.
Several methods are available at the stage of study design (restriction,
randomization and matching) to minimize the confounding effect of potential
confounders. At the analysis stage, if there are a limited number of confounders,
the Mantel-Haenszel approach of computing adjusted odds and risk ratios can be
employed. But if the number of potential confounders is large, and the outcome of
interest is dichotomous, the unconditional or conditional multiple logistic
regression approach is the method of choice.
40
I will discuss a little about the multiple logistic regression because it is in common
use today epidemiologic investigations and many epidemiologic outcomes are
dichotomous. Furthermore, it is easier to understand the coefficients and the odds
ratios than many outputs in other types of transformation. The logit transformation
is more suitable for modelling as it produces values ranging from minus infinity
(when p=0) to infinity when (p=1). In the logistic equation, the probability of a
disease given variables X1, X2 and Xn is given as
f (x) =
1
-
1+ e
a + β X +β X +β X
1
1
2
2
n
n
And the logit (p/1-p) = a +ß 1X1+ß2X2+ßnXn
where ß’s are the coefficients denoting the magnitude of the increase/decrease in
log odds produced by one unit increase in the independent variable (continuous
independent). For categorical variables, the coefficient represents the difference
between level 1 and level 0 (reference category). The anti-logs of the coefficients
are the odds ratios which have the familiar interpretation.
If the outcome of interest is quantitative, then the conventional multiple regression
is the alternative. When considering multi-dimensional contingency tables, the
log-linear models approach can also be adopted to assess confounding.
Effect Modification (Interaction)
Apart from confounding, there may be an interaction (effect modification) between
the exposure and other variables which may becloud the exact contribution of the
exposure variable. It has been shown for example that aspirin protects against
heart attacks, but only in men and not in women. Thus gender is an effect modifier
in this association because the effect is different in the different sexes. It will be
difficult to present in this lecture, a comprehensive discussion on bias,
confounding, chance and effect modification, but let it be known that
epidemiologists and biostatisticians have techniques for dealing with these so that
the truth will be told. This is what I have enjoyed doing for so many years!
When the above issues have been addressed in a particular study, other conditions
must be considered before establishing a cause-effect relationship. These criteria
are generally referred to as Hill’s postulates. They include the strength of
association, the consistency of association, biologic plausibility, the temporal
relationship and the dose-response relationship.
41
Who is an Epidemiologist?
From what I have presented thus far, I can assume that you already know who
epidemiologists are and what they do. According to Porta et al, 2014, an
epidemiologist is a professional who strives to study and control the factors that
influence the occurrence of disease or health-related conditions and events in
specified populations and societies; has an experience in population thinking and
epidemiologic methods, and is knowledgeable about public health and causal
inference in health.
What is Public Health?
Mr Vice Chancellor Sir, I have talked about epidemiology. I have mentioned in
passing medical statistics, let me say that these two are handmaidens for Public
Health. Public Health has been defined as “The science and art of preventing
disease, prolonging life, and promoting health through organized efforts of society
(. Although Public Health activities change with changing era, technology and
social values, it remains a combination of services and programmes aimed at
preventing diseases in populations, preventing premature death, injuries, diseaseassociated discomfort and disability thus enabling people to live longer healthy life
years. Examples of Public Health activities include: water and environmental
sanitation, vaccination, family planning services, pollution control, health
promotion, etc. In order to accomplish these, Public Health adopts a general
approach summarized in the schema below.13
The first step in Public Health policy and action is to identify the health problems
of the population of interest. The population may be a village, a settlement, a local
government area, a state, an institution, a country, etc. This stage answers the
questions Who, Where, When, What and How? At the stage of problem
identification, public health relies on disease surveillance, disease outbreak
investigation, and descriptive studies. At the stage of risk factor identification
analytic epidemiologic enquiries are sine qua non. At the stage of evaluating
interventions, randomized controlled trials and quasi-interventions are critical
while at the stage of implementation, evidence-based decisions are necessary. In
each of these stages, epidemiology is the foundation and thus the beginning of
wisdom.
Public Health Approach
13
Source: Caldwell, 2006
42
In summary, Public health is concerned with health of the public; i.e., populations.
Epidemiology is the method/strategy of studying disease/health in human
populations. Epidemiology is therefore the beginning of wisdom in this
endeavour. Let me end this section with the words of William Bruce Cameron
(1963) which is often credited to Albert Einstein “not everything that counts can be
counted, and not everything that can be counted counts. Epidemiologists seek what
counts by sorting out what has been counted.
The Status of Epidemiology Manpower Development:
Mr. Vice Chancellor, just six years ago we looked at the educational and
professional qualification of State Epidemiologists and Avian Influenza Desk
Officers from 34 states of the federation. We found that only 3 of the 52
respondents (5.8%) had a specialized training (Masters degree or equivalent) in
Epidemiology and none held a PhD. In 2007, AfriHealth estimated that about 50
academic institutions in the AFRO region were providing graduate-level training in
Public Health and that doctoral programmes or other higher-level training in
epidemiology is scarce (Nachega et al., 2012). In various Departments of
Community Health/Medicine across the country where epidemiology and control
of communicable diseases are taught, we can only boast of a handful of teachers
Implementation
How do you do it?
Intervention evaluation
What works?
Risk factor
identification:
What is the cause?
Surveillance:
Descriptive studies
What is the problem?
Response
response
Problem
Figure 27: The Public Health Approach.
with specialized training in Epidemiology. Currently, Federal Ministry of Health in
partnership with the U.S. Centers for Disease Control and Prevention (CDC) is
43
training middle-level practicing epidemiologists through the Nigeria Field
Epidemiology and Laboratory Training Programme (NFELTP).
44
MY CONTRIBUTIONS TO PUBLIC HEALTH
Establishing a Disease Surveillance and Notification in Nigeria
Prior to 1988, there was no unified functional system of disease surveillance in the
country. States that had some semblance of surveillance submitted very scanty
reports at irregular intervals and many others did not submit at all. In November
1986 a large outbreak of yellow fever occurred in many states of the Federation
affecting 10 of the then 19 States. The most heavily affected were the states of
Oyo, Imo, Anambra, and Cross River in the south, Benue and Niger in the middle
belt, and Kaduna and Sokoto in the north. This epidemic took health authorities
unawares and it continued for months without being recognized thus resulting in
several hundred deaths. Following this, a National Task Force on Epidemic
Control was set up to find a lasting solution to this sad and sorry situation. The
National Task Force identified poor disease surveillance and notification as a
major constraint to effective disease control in Nigeria and therefore formed an ad
hoc sub-committee that was mandated to develop a system of disease surveillance
for the country.
Mr. Vice Chancellor Sir, permit me to say that I was privileged to be a key
member of that committee. The Chairman of that committee was Professor
A.B.O.O Oyediran, of UCH Ibadan and a former Vice Chancellor of the University
of Ibadan. Other members included Profs Olanipekun Alausa, former Provost of
Ogun State University College of Medicine (now Olabisi Onabanjo University,
College of Medicine), and Oyewale Tomori, former VC of Redeemer’s
University, Dr (Mrs) Ojo and the then Chief Consultant Epidemiologist, Dr (Mrs)
Asagba.
45
Figure 28: Pioneers of disease surveillance in Nigeria
Between 1988 and 1989, we developed a unified and functional disease
surveillance and notification system in the country which was approved and
adopted by the National Council on Health in 1990. We wrote a training manual
which became the Bible on Disease Surveillance and Notification in Nigeria.14
Between 1989 and 1992 several training workshops were organized at the Local
Government, State and Federal levels.
14
Oyediran ABOO, Tomori O, Ekanem EE. Asagba AO, Ojo OO and Van-Vliet H (1989) Surveillance and
Notification of Diseases in Nigeria. Federal Ministry of Health, Nigeria.
46
As the youngest member of the team then, I enthusiastically handled many aspects
of the training on disease surveillance and notification. From 2001 to 2010 I was
the Integrated Disease Surveillance and Response (IDSR) coordinating Committee
Chairman. Today I am proud that Nigeria is one of the countries in Africa that has
a uniform system of disease surveillance and notification. There are structures for
disease surveillance in almost all public health facilities in the country. All States
and Local Government Health offices have designated focal persons on Disease
Surveillance and Notification.
Investigation of Epidemics
Prior to 1989, the Epidemiology Division of the Federal Ministry of Health did not
have standard guidelines on how to investigate outbreaks in the country.
Investigations of outbreaks were left to conjecture. We therefore worked with the
Federal Ministry of Health to develop a textbook- like training manual titled
“General Epidemiology and Investigation of Disease Outbreak. This text also
served as a bible on epidemic investigations in those days. We were able to build
the capacity of Federal, State and Local government health workers in the art of
epidemic investigation. I am happy to have been a part of that process. I am not too
47
happy that this book has almost disappeared from State Ministries of Health and
Local Government Health Departments.
Estimating HIV/AIDS Magnitude and Trends
Since 1995, I have been involved in assessing and strengthening HIV/AIDS
surveillance systems in a number of countries such as Nigeria, Botswana, Namibia,
Swaziland, Lesotho and Somalia. I have also been directly responsible for
developing and managing the HIV/AIDS/STI surveillance system in Somalia and
training of senior HIV/AIDS staff on Second Generation HIV/AIDS surveillance
in Ghana. In Nigeria I have been involved in all the HIV sentinel sero-prevalence
surveys from 1996 to 2010, a period of about 14 years.
In the early years of the HIV/AIDS pandemic, one of the challenges facing
national programmes was knowing the magnitude of the problem in their
respective countries. By the early 1990s the World Health Organization had
developed a statistical modelling software (EPIMODEL) to estimate HIV/AIDS
burden in different countries.
In the absence of this software, I used a direct standardization procedure to
estimate from sentinel data, the number of people aged 15-49 years with
HIV/AIDS in Nigeria. When the WHO team came to Nigeria in 1999, I presented
our estimates to them.
Mr. Vice Chancellor sir, I am proud to say there was a high degree of agreement
between our estimates and the WHO EPIMODEL. It was that estimate of 2.6
million people that was used as the basis for making subsequent projections for the
country. I have used similar approaches to derive estimates for Botswana. This
estimate and the results of the 1999 sentinel survey which showed a HIV
prevalence of 5.4% (among women aged 15-49 years) was formally presented to
the Presidency by an FMOH team, led by Dr. Sani Gwarzo. This presentation was
well received by the Presidency. It may have contributed to some extent, in the
greater commitment by the federal government to the fight against the HIV
epidemic in Nigeria. In Botswana, our team, to our knowledge, was the first to
report the stabilization of the HIV/AIDS epidemic in the Sub-Saharan Africa.
48
Figure 29: Trend in HIV prevalence among Botswana pregnant women, 1992-2005
Training of Specialists in Public Health
Mr Vice Chancellor Sir, the Department of Community Health was the first to
establish a postgraduate training in Public Health (MPH) in the whole of West
Africa in 1982 (credit to Prof. O. O. Hunponu-Wusu). This was one year before I
joined the department as young lecturer. Since then the Department has produced
over 1000 specialists in Public Health (about 200 specializing in Epidemiology at
the Masters level) and I have had the opportunity of supervising over 150 of them.
Between Mr Vice Chancellor, there are grandmothers and grandfathers. I am proud
to say that I am a grand-teacher, a teacher of teachers. Many of my students are
now Professors, Associate Professors and Senior Lecturers. They are too numerous
to count. Among them we have in this audience Prof Bayo Onajole, Associate
Professor Victor Inem, Associate Professor Kofo Odeyemi, Associate Professor
Babatunde Ogunnowo, Dr Alero Roberts, Dr Oridota, Dr Sekoni, Dr Odukoya, Dr
Olufumilayo and others. Many of my students are Professors in Universities across
the country while others are working with International Agencies such as the
World Health Organization, UNICEF, UNAIDS, etc. I am proud to announce that
one of them, Dr Michael Gboun who is now UNAIDS Country Director in Sierra
Leone is here. He came all the way from Sierra Leone to part of this occasion.
One of my aspirations has been to produce PhD graduates in Epidemiology. Mr
VC sir, I am proud to say that in December last year, Dr Bernadine Ekpenyong of
49
the Department of Public Health, University of Calabar, who was directly under
my supervision, successfully defended her PhD Public Health (Epidemiology)
thesis.
CONTRIBUTION TO KNOWLEDGE
Mr VC Sir, my contributions to knowledge have been in areas of Diarrhoeal
Diseases, HIV/AIDS, Influenza and Reproductive Health Epidemiology. I have
also collaborated with colleagues in various Departments such as O&G, Surgery,
Radiotherapy, Paediatrics and Dentistry; applying my expertise in Epidemiology
and Biostatistics to research in other medical/ health issues.
Diarrhoea in Children in Day care Centres:
In the 1980s and early nineties, diarrhoeal diseases were the major killers of
children under 5 years not only in developing countries but also in developed
countries. At that time there were several epidemics of diarrhoea in communities,
and in institutional settings such as day-care centres and nurseries. My first
epidemiologic work was to investigate the transmission dynamics of diarrhoeapathogens in day-care centres in order to interrupt the transmission pathways.
Working with a renowned Professor of Infectious Diseases and Clinical
Microbiology, Dr Hebert DuPont, of the University of Texas Medical School in
Houston, a grant from the NIH enabled me to undertake systematic studies of
diarrhoea transmission pathways among children in five day care centres in
Houston, Texas.
I collected and analyzed stool samples, air samples and environmental samples for
enteric bacteria. I compared isolation rates of enteric bacteria during routine
sampling and during diarrhoea outbreaks. Faecal coliforms were recovered from
hands of staff with significantly greater frequency during diarrhoea outbreaks than
during non-outbreak periods. We found that enteric pathogens were transmitted
from diaper change areas through contaminated hands of staff, communal toys and
other classroom objects. We therefore recommended interruption of transmission
through rigorous hand-washing and disinfection of specific locations in day care
centres. This study formed the basis of another study to examine whether these
recommendations eventually would lead to reduction of diarrhoea incidence in
these day-care centres. By the time this study was conducted I had already
graduated and left the U.S.
50
Table 3: Comparison of faecal coliform isolations during outbreaks and routine sampling
Rates of faecal coliform isolation
(%)
Outbreaks
Routine sampling
Statistical significance
27/119 (23)
4/33 (12)
χ2=1.78, p=0.200
20/49 (41)
2/16 (13)
χ2=4.32, p=0.026
7/70 (10)
2/17 (12)
p=0.563*
26/70 (37)
3/21 (14)
χ2=3.89, p=0.049
Day care centre
2
Source of sample
All environmental Samples
Classroom objects
Toilet areas only
Hands
3
All environmental Samples
Classroom objects
Toilet areas only
Hands
25/85 (29)
18/39 (46)
7/46 (15)
23/55 (42)
5/35 (14)
3/19 (16)
2/16 (13)
5/27 (19)
χ2=2.72, p=0.100
χ2=5.10, p=0.024
p=0.577*
χ2=4.37, p=0.039
4
All environmental Samples
Classroom objects
Toilet areas only
Hands
5/33 (15)
3/15 (20)
2/18 (11)
23/55 (21)
6/67 (9)
3/24 (13)
3/43 (7)
14/73 (19)
p=0.319*
p=0.42*
p=0.462*
χ2=0.08, p=0.863
5
All environmental Samples
Classroom objects
Toilet areas only
Hands
*Fisher’s exact test
7/32 (22)
4/15 (27)
3/17 (18)
2/18 (11)
0/16 (0)
0/8 (0)
0/8 (0)
0/10 (0)
p=0.046*
p=0.154*
p=0.296*
p=0.405
In the Lagos University Teaching Hospital, I undertook a study to determine the
causes of death among children between 1987 and 1988. The results are shown in
Table 5.
51
Table 4: Proportionate Mortality Ratio (PMR) of Causes of Post-Neonatal Deaths, LUTH,
Lagos. May 1987-April 198815
Causes of death
Gastroenteritis
Marasmic Kwashiorkor
Bronchopneumonia
B.I.D.
Meningitis
Prematurity
Severe Anaemia
Marasmus
Septicaemia
Others and unspecified
Total
Number of deaths
40
31
24
23
12
11
9
8
6
108
272
PMR
14.7
11.4
8.8
8.4
4.4
4.0
3.3
2.9
2.2
39.7
100.0
It was found that gastroenteritis was the leading cause of death accounting for a
proportionate mortality ratio of 14.7%. This called for the attention of
paediatricians and hospital authorities to the growing problem of diarrhoea in
children and the need for improved management.
Diarrhoea in Children (Community Level)
Although the diarrhoea in children was a global problem, I believed in the strategy
of “Think globally, but act locally”. I therefore started investigating diarrhoeal
diseases in Iwaya Community.
Most of my work then was
supported by the Harvard
Institute for International
Development (HIID) through
the Applied Diarrheal Disease
Research Project (ADDR). At
this point I would like to say
that the HIID, through the US
Embassy provided a lot of
financial and technical support
for our research projects. One
of such support was the
provision of an IBM desktop
computer. It may interest this
15
Ekanem, EE. Causes of neo-natal and post neonatal mortality in Lagos University Teaching Hospital
52
audience to know that the presentation of the desktop was a very significant event
in the College at that time. This event was carried in many national dailies. At that
time, only a handful of lecturers could boast of owning a computer.
This computer enabled us to analyse our research data with ease. The system was
also used to assist other colleagues in analysing their data.
53
Our studies focused on acute and prolonged diarrhoea (> 7 days). In our first
investigation in Iwaya community we studied 267 children and we found that
diarrhoea was the leading cause of morbidity among children under five
accounting for a PMR of 40% with an incidence of 1.6 episodes per child per year.
Upper respiratory infections and malaria were the other major causes of illness
among these children. Enteric pathogens were isolated from 36% of the specimens
and Enteropathogenic E.coli (EPEC) was the most frequently isolated pathogen.
We recommended further studies to investigate human behaviour and practices
associated with increased risk of diarrhoea among children in the community.
Subsequently, we therefore undertook a study to investigate the possible
determinants of diarrhoea in this community. We followed a total of 623 children
for three and a half months and used a nested case-control approach together with
ethnographic methods to examine the role of environmental and behavioural risk
factors. We found that there were many environmental and behavioural risk factors
that contributed to the incidence of acute diarrhoea in this community. These
included the habit of storing chamber pots popularly referred to as “po” in the
same room with cooking utensils, and defecating in chamber pots inside the house
as well as the indiscriminate unsanitary disposal of refuse, etc.
Table 5: Significant risk factors for childhood diarrhoea in Iwaya Lagos16
Risk factor
Storing food in the same room with
defaecation bowl
Cases
23/38
(60.5)
Controls
42/110
(38.2)
RR
95% CI
2.5 1.09-5.67
p
.03*
Feeding index child with left-over >6
hours
11/67
(16.4)
14/206 (6.8)
2.7 1.07-6.71
.03
Defaecating in chamber pots inside
the house
33/67
(49.3)
69/206
(33.5)
1.93 1.06-3.50
.03*
Water from tap outside dwelling unit
52/67
(77.6)
105/206
(50.9)
3.3 1.69-6.63
.001
Disposing of refuse in the open
29/67
(43.3)
39/206
(18.9)
3.3 1.72-6.19
.001
Mother works outside the home
24/66
(36.4)
30/206
(14.8)
3.3 1.66-6.50
.001
Presence of faeces in the toilet
area/bowl
34/67
(50.7)
70/206
(34.0)
2.1
16
1.1-3.60
Ekanem EE, Akitoye Co and Adedeji OT (1991). Food hygiene behaviour and the risk of childhood
diarrhoea: A case-control study. Journal of Diarrhoeal Disease Research 9: 219-226.
54
.02
*still significant after controlling for confounders
Prolonged Diarrhoea in Children:
Furthermore we observed in the Iwaya community that while many of the
diarrhoea episodes were of acute nature, some children had diarrhoea which lasted
for more than 7 days (which we referred to as prolonged diarrhoea). Prolonged
diarrhoea in children is of particular concern because it contributes significantly
diarrhoea-related deaths. We therefore undertook a study to investigate the possible
determinants of prolonged diarrhoea in this community.
We found no association between domestic, environmental and personal hygiene
practices and the risk of prolonged diarrhoea. A significant higher risk of
prolonged diarrhoea was found among children who were mainly fed with foods
bought from street vendors and those who were fed with ogi (a maize pap) as the
main diet. We concluded that foods bought from street vendors may serve as one
possible source of diarrhoeal diseases in Iwaya and diarrhoea episodes could be
prolonged following repeated exposures especially in children who are fed with
low-energy and low nutrient density diet. We suggested that other factors such as
use of antibiotics, animal milk products and nutritional status should also be
evaluated in further studies of prolonged diarrhoea.
Table 6: association between child-feeding practices and the risk of prolonged diarrhoea in
children 6-36 months
Practice
Cases n=0
Hand feeding of child
3/6 (50.0)
Controls
n=206
22/57 (38.6)
Crude
M-H
odds ratio odds ratio
1.59
1.54
95% CI
0.22-10.89
Feeding child food bought from
street vendors
13/20 (65.0) 79/206 (38.3)
2.98
2.91
1.03-8.57*
Child eats with unwashed hands
8/20 (40.0) 67/206 (32.5)
1.38
1.32
0.47-3.75
Feeding child ogi as main diet
8/12 (66.7) 40/126 (31.7)
4.30
4.13
1.05-17.85*
Feeding child with leftover foods
2/20 (10.0)
1.52
1.70
0.24-9.0
14/206 (6.8)
*still significant after controlling for confounders
Mr Vice Chancellor, back in 1990s when diarrhoea was killing thousands of our
children daily, the use of oral dehydration solution was widely advocated globally.
In Nigeria however, as a matter of government policy, pre-packaged ORS was not
generally made available to mothers and care-givers. Mothers were asked to
prepare the salt-sugar solution at home using a prescribed recipe. The pre-packed
55
ORS was restricted for use at health facilities. It was generally claimed that
mothers knew how to make the solution because they could recite the prescribed
recipe. We undertook a study of 274 mothers to determine quantitatively (through
laboratory chemical analysis) and qualitatively their ability to prepare the saltsugar solution in the usual home environment. We found that only about 7% of
mothers prepared solutions within acceptable sodium and glucose levels. We
concluded that salt-sugar solutions prepared by Nigerian mothers were not safe.
We recommended that pre-packaged ORS should be made accessible to mothers
and that messages and strategies for promoting home-made SSS should be
modified in order to avoid the dangers associated with improperly constituted
solutions.
Table 7: Field assessment of the salt-sugar solutions prepared by mothers
Practice
Too much salt
Not enough salt
Right amount of salt*
No of mothers
43
21
39
%age
41.7
20.4
37.9
Too much sugar
Not enough sugar
Right amount of sugar*
12
53
58
11.7
51.5
36.9
Too much water
Not enough water
Right amount of water*
0
8
95
0.0
7.8
92.2
*Right amount of salt = one level teaspoon
*Right amount of sugar = 10 level teaspoon of granulated sugar or 9 cubes of sugar
*Right amount of water = 600ml (0ne standard beer bottle or two bottles of soft drink)
56
Table 8: Distribution of sodium and glucose concentrations in SSS prepared by Nigerian mothers
Concentration (mmols/l)
Sodium
No. of samples (%)
Glucose
No. of samples (%)
0-49
2
(1.9)
51
(49.5)
50-100
7
(6.8)
22
(21.4)
69 (67.0)
28
(27.2)
101-200
201-250
1
(1.0)
2
(2.0)
251-300
4
(3.9)
0
(0.0)
301-350
4
(3.9)
0
(0.0)
>350
16 (15.5)
0
(0.0)
Total
103 (100.0)
103 (100.0)
Food Poisoning through hospital food handlers
Because of the danger posed by food handlers in the transmission of food
poisoning and other intestinal disorders, we evaluated the knowledge and practices
of 161 hospital food handlers in two tertiary hospitals in Lagos. We also processed
stool samples for enteropathogens and evaluated nasal samples for the presence of
staphylococcus aureus.
Table 9: Prevalence of enteroparasites among hospital food handlers
Isolates
One ova type present
Multiple ova present
Ova + protozoa
Protozoa alone
E.histolytica cyst
Shigella spp
Salmonella spp
*Results not recorded for 17 specimens
Hospital A (n=14)
No positive (%)
32 (28.1)
14 (12.3)
1 (0.8)
3 (2.6)
1 (0.8)
2 (1.7)
0 (0.0)
Hospital B (n=20)
No positive (%)
9 (30.0)
2 (6.7)
1 (3.3)
1 (3.3)
0 (0.0)
1 (3.3)
0 (0.0)
Total (149)*
No (%)
41 (28.5)
16 (11.1)
2 (1.3)
4 (2.8)
1 (0.7)
3 (2.1)
0 (0.0)
Although almost all the food handlers claimed to routinely wash their hands at
different stages of food preparation, only 28.6% of them actually did so from direct
observation. The nasal carriage of staphylococcus aureus was 24%. Different
enteropathogens were isolated from stool samples. We recommended that there
should be continuous medical surveillance of this group of hospital employees and
57
that periodic in-service programme on food safety and hygiene should be
introduced among them.
Asthma in children
We conducted a case-control study17 among 280 (140 asthmatic and 140 controls)
to examine environmental factors for childhood asthma. We found a statistically
significant positive association between household pets, parents’ cigarette
smoking, use of mosquito coils, presence of rodents and the occurrence of asthma
in children. We also found a protective effect of indoor plants, and an unexplained
significant association with cosmetic aerosols. We recommended that measures to
reduce allergens and aero-irritants in the home should be adopted particularly in
homes with known asthmatic children.
17
Fagbula D and Ekanem EE (1994). Some environmental risk factors for childhood asthma: A case –control
study. Annals of Tropical Paediatrics 14: 15-19
58
Table 10: Association between Asthma and Aeroallergens
Environmental factors
Cases
n=140
119
Controls
n=140
47
Odds
ratio
11.2
Household pets
138
52
116.8
117.5 (46.9-256.5)
<0.001
Rodents/cockroaches
139
77
113.7
121.0 (40.9-358.1)
<0.001
Indoor biomass smoke
99
113
0.6
0.148 (0.07-0.30)
<0.001
Mould growth elsewhere
54
79
0.5
0.48 (0.295-0.794)
0.004
Cigarette smoking (parent)
81
55
2.1
1.41 (0.84-2.36)
0.002
Cosmetic aerosols
37
53
0.6
0.61 (0.35-1.04)
0.041
Mosquito coils
93
49
3.7
3.67 (2.23-6.03)
<0.001
Indoor plants
41
63
0.5
0.48 (0.28-0.82)
0.007
Damp mouldy bedrooms
Adjusted OR with
Significance
95% CI
(p)
10.9 (6.4-18.87)
<0.001
Prevention of Mother-to-child-Transmission of HIV (PMTCT)
In the early phase of the PMTCT implementation in Nigeria, we conducted a study
among 345 pregnant women attending antenatal clinics the two tertiary hospitals in
Lagos. It was undertaken to determine their knowledge on PMTCT and
acceptability of HIV voluntary counselling and testing in pregnancy as a strategy
for the prevention of mother-to-child transmission (PMTCT) of HIV. The results
showed that majority of the pregnant women had very good knowledge of the
modes of HIV transmission. However, knowledge of specific aspects of MTCT
such as transmission of the virus from mother to child during pregnancy, delivery
and breastfeeding was generally lower. Specifically, only a little over half of the
respondents were aware of the fact that HIV could be transmitted through breast
milk (Table 11). We therefore recommended that issue of HIV transmission
through breast milk represents an area where more attention and awareness was
required in the PMTCT programme in Nigeria.18
Table 11: Knowledge of respondents on mother-to-child transmission of HIV
Knowledge Statement
HIV can be transmitted from HIV-infected mother
to her baby
18
Yes
No
Don't Know
322 (93.3)
18 (5.2)
5 (1.4)
Ekanem EE and Gbadegesin A. (2004) Voluntary counselling and testing for Human Immune Deficiency Virus:
A study on acceptability by Nigerian women attending antenatal clinics. African Journal of Reproductive Health 8:
91-99
59
Through breast milk
201 (58.3)
77 (22.3)
67 (19.4)
To unborn child in the womb
196 (56.8)
104 (30.1)
45 (13.0)
During delivery
105 (30.4)
116 (33.6)
124 (35.9)
97.2
100.0
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
95.0
83.0
75.0
No formal
education
Primary
Secondary
Tertiary
Figure 30: Knowledge score on HIV transmission modes by respondents' level of education
Knowledge of transmission of HIV and sexually transmitted infections (STI)
We undertook a study among 395 commercial bus drivers and attendants in Lagos
to ascertain the knowledge on sexually transmitted infections including HIV/AIDS,
including sexual practices and in particular the use of condoms. We found that
these men had a strongly woven network of sexual relationships. This network
included apart from their wives, commercial sex workers, young female hawkers in
an around the parks, school girls, market women in and around the parks. More
than two-thirds of them had multiple sex partners and specifically more than half
patronized commercial sex workers. There was a marked gap between patronage of
commercial sex workers (CSW) and condom use. Almost all of them perceived
themselves to be at risk of acquiring STIs but 88% felt it was impossible for them
to “catch AIDS”.19 We noted that bus drivers and their attendants are important
19
Ekanem EE, Afolabi BM. Nuga AO and Adebajo SB (2005). Sexual behaviour, HIV-related knowledge and
condom use by intra-city commercial bus drivers and motor park attendants in Lagos, Nigeria. African Journal of
Reproductive Health, 9 (1): 79-85.
60
bridge populations that play a major role in propagating HIV in urban settings. We
therefore called for specific intervention programmes targeting these men and
other similar high risk groups.
70
60
50
40
30
20
10
0
15 - 19 years
20 - 29 years
30 - 39 years
Patronage of CSW
40 - 49 years
50 and over
Current condom use rate
Figure 31: Age-specific patronage of female sex workers and current condom use rate by intracity bus drivers/attendants in Lagos
Influenza
Between April 2009–August 2010, our research team (under direct funding from
the U.S Centers for Disease Control and Prevention) tested 2803 patients for
influenza viruses and 217 (7.7%) were positive for influenza viruses. The isolation
rate was 8% and 5% for ILI and SARI patients respectively. During the prepandemic period, subtype H3N2 (A[H3N2]) was the dominant circulating
influenza A virus subtype. The 2009 pandemic influenza A virus subtype H1N1
(A[H1N1]pdm09) replaced A(H3N2) as the dominant circulating virus during
November 2009. Among persons with ILI, A(H1N1)pdm09 was most frequently
found in children aged 5–17 years, whereas among subjects with SARI, it was
most frequently found in persons aged ≥65 years. The percentage of specimens that
tested positive for influenza viruses peaked at 18.9% in February 2010, and the
majority were A(H1N1)pdm09. We concluded that Influenza viruses were
associated with ILI and SARI in Nigeria. We recommended that continuous
surveillance of influenza viruses be maintained so as to enable us better understand
the epidemiology and seasonality of influenza viruses in Nigeria.
Table 12: Prevalence of influenza viruses in Nigeria
Number or Number (%) of patients by site
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Characteristic
Tested specimensa
Kano
792
Abuja
786
Nnewi
553
Lagos
615
83 (10.5)
54 (6.9)
44 (8.0)
36 (5.9)
55 (69.5)
50 (92.6)
41 (93.2)
33 (91.7)
28 (35.3)
4 (7.4)
3 (6.8)
3 (8.3)
A(H1N1)pdm09
28 (50.9)
39 (78.0)
23 (56.1)
10 (30.3)
A(H3N2)
16 (29.1)
9 (18.0)
13 (31.7)
14 (42.4)
A(H1N1)
5 (9.1)
0 (0.0)
2 (4.9)
4 (12.1)
6 (10.9)
2 (4.0)
3 (7.3)
5 (15.2)
Tested specimens positive for influenza
Influenza virus type detected
b
Influenza A virus
Influenza B virus
Influenza A virus subtype detected
c
Unable to subtype
Abbreviations: A(H1N1), influenza A virus subtype H1N1; A(H1N1)pdm09, 2009 pandemic influenza A virus
subtype H1N1; A(H3N2), influenza A virus subtype H3N2.
a
Samples from 58 patients did not include submitting site information.
b
Denominators are no. of specimens that tested positive for influenza viruses.
c
Denominators are no. of specimens that tested positive for influenza A viruses.
Reproductive Health Epidemiology
In the last couple of years, I have been working closely with The Campaign
Against Unwanted Pregnancy (CAUP), a non-governmental organization, in Lagos
under the leadership of Prof Boniface Oye-Adeniran, Department of Obstetrics and
Gynaecology. This NGO has undertaken numerous community-based studies on
various aspects of reproductive health, including prevalence and determinants of
unwanted pregnancy, adolescent sexuality, contraceptive prevalence, maternal
mortality, etc. My contributions in these studies have been in the area of study
design, statistical analysis and report writing.
To avoid duplication of
presentations, I have decided that I leave the far-reaching results of these studies
for Prof. Oye-Adeniran (the Principal Investigator). Let me however wet your
appetite by revealing that many of our women are still experiencing unwanted
pregnancy. Many are still dying from causes related pregnancy and child birth.
The 2010 maternal mortality ratio for Lagos State of 450 per 100,000 live births
(95% CI of 360 and 530) is still unacceptably high. This calls for fast-tracking of
strategies for improved maternal health services in the State in order to attain the
sustainable development goal target of reducing global maternal mortality to less
than 70 per 100,000.
CONCLUSIONS
In the book of Psalms 111:10, we read that the “fear of the Lord is the beginning of
wisdom”. This bible passage simply means that one must have reverence for our
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Creator, recognize his grandeur, and appreciate His infinite power and our own
littleness so that we can be teachable in order for our footsteps to be properly
directed. In the same vein, if we want our footsteps to be properly directed in
Public Health, if we wish to be wise in Public Health decisions and actions, then
we must begin with Epidemiology.
63
RECOMMENDATIONS
Federal Government
In Nigeria today health data which are generated from various sources such as
national surveys, Integrated Disease Surveillance and Response (IDSR) disease
outbreak investigations, hospital morbidity and mortality, etc. are difficult to come
by. There is no central repository for health data. The Federal government should
establish a National Centre for Health Statistics situated within the Nigeria Centre
for Disease Control (NCDC). This centre would serve as repository of information
on health that should guide the nation on policies and actions aimed at improving
the health of Nigerians.
The current training of Field Epidemiologists in the country is funded by the U.S.
Centers for Disease Prevention and Control with negligible input from the Federal
Government. The Federal Government should make special provision to support
this noble cause. The Nigeria Centre for Disease Control (NCDC) can take over
this programme if adequately funded.
Non-Governmental Organizations
NGOs in Nigeria should be encouraged to support Disease Surveillance and
Notification in the country. Furthermore, they should actively undertake and
support other means of data collection on health indices in the country.
The University of Lagos
Public Health is a multidisciplinary field. The present medical non-medical
dichotomy is not healthy for Public Health development and training in the
country. The University of Lagos should make every effort to ensure that nonmedical teachers in clinical departments are accorded equal opportunities in the
University system as their medical counterparts. Failing to do so, the University of
Lagos may find it difficult to become a centre of excellence as far as Public Health
training is concerned.
The University should recognize and support the “Epidemiology and Biostatistics
Unit” as one of the academic units in the University. This unit can provide
epidemiologic and statistical support to the research community of the College thus
enhancing its visibility through high quality research and publications.
ACKNOWLEDGEMENTS
Mr Vice Chancellor Sir, charity they say, begins at home. My home in this context
is the Department of Community Health and Primary Care. I must use this
opportunity to appreciate the first Head of Department under whom I worked, in
the person of Prof. O. O Hunponu-Wusu. Prof Hunponu-Wusu was the person
64
who, for some reason believed in me and advised me as a father on both academic
and family matters. Prof was very passionate about Public Health generally and
Epidemiology in particular. This may have prompted him to recruit a young
epidemiologist to strengthen the then newly established MPH programme. Prof
Hunponu-Wusu was a father to whom I could go to at any time to discuss personal
matters.
I consider myself lucky to have worked with many wonderful Heads of
Department, Professors Muriel Oyediran, Dorothy Ogunmekan and Akin
Osibogun. They gave me the necessary support and an enabling environment to do
my work. I say a big thank you. May your paths continue to be bright.
My other Heads of Department, Prof Bayo Onajole, Dr Babatunde Ogunnowo, Dr
Victor Inem and Dr. Kofo Odeyemi are a special breed. They were all my students
and I am very proud of them. They have all accorded me the respect and regard of
being their teacher and this is one reward I enjoy on earth while waiting for the
teacher’s reward in Heaven. I do not remember their scores in Epidemiology and
Biostatistics but I want to believe that they all did well otherwise they could have
dealt with me according to the multitude of my iniquities when they became Heads
of Department. I have indeed enjoyed working with each and every one of them.
I appreciate the support and cooperation of all academic and non-academic
members of our Department; particularly, my colleagues in the Epidemiology and
Biostatistics Unit who are overworked, underpaid and rarely appreciated. These are
Prof Onajole, Drs Odukoya, Oridota, Sekoni and Mr Akinsola. In particular I have
been overwhelmed by the immense show of solidarity from members of the
Inaugural Lecture Planning Committee of the Department in the persons of Dr
Ezekiel Oridota, Mr Oluwatosin Akinsola, Dr Bolanle Johnson, Dr Oluwakemi
Odukoya, Dr Temitope Ladi-Akinyemi, Dr Oluchi Kanma-Okafor and Dr
Adedoyin Ogunyemi who worked tireless to see to success of this occasion. May
the Almighty meet you all at the point of your need.
I must single out Dr Alero Roberts and Dr Kofo Odeyemi, who assisted with the
editing and formatting of the manuscript. May the Almighty send help to you in
your time of need.
I want to publicly acknowledge my colleague and sister, Dr C. O. Akitoye who
was a key member of our Diarrhoeal Disease Research team. She is a woman who
always brought down my blood pressure at any time. She did not allow me to be
discouraged when our take-home pay could not take us home. She made me
65
appreciate the socio-cultural context of medicine generally and of epidemiology in
particular. Thank you my sister.
My profound gratitude goes to all the former provosts of the College of Medicine,
University of Lagos. In particular I must mention Professors Akinosi, Sofola, and
Tolu Odugbemi who did not mind my constant requests for permission to be away
but gave the necessary support and encouragement. At the height of my
engagements with the World Health Organization assignments, Professor Sofola’s
wife was heading the Tuberculosis and Leprosy programme in the Federal Ministry
of Health. Little did I know that the Sofola in the FMOH was related to the Sofola
in the College of Medicine. Each time I visited the WHO office, (then located on
the same floor with the Tb and Leprosy programme), the information will filter to
the Provost. I was surprised one day when Prof Sofola referred to me as this
“W.H.O. man”. Even then he did not withdraw his support. Thank you Sir. But let
me confess that since then I began to reduce my visits to WHO office.
I want to thank the current provost Prof. Folashade Ogunsola, a woman of
substance, a woman of character, a woman who has shown that what a man can do,
a woman can do even better. Thank you ma’am for your support.
Mr Vice Chancellor Sir, your carriage, charisma and humility has taught me many
lessons. Thank you for the support that I have enjoyed during your tenure. Thank
you for approving the date for this lecture. I believe that it is your personality and
the way you relate with colleagues that has witnessed the significant improvement
in attendance at Senate meetings.
My supervisors for my PhD research work, Dr Beatrice Selwyn, Associate
Professor of Epidemiology, Dr Mort Hawkins, Professor of Biometry (University
of Texas, School of Public Health) and Prof. Hubert DuPont, Professor of
Infectious Diseases and Clinical Microbiology (University of Texas Medical
School) were wonderful people. Dr Selwyn was my mentor in Epidemiology, Dr
Hawkins inspired me to develop interest in Biostatistics while Dr DuPont steered
my path towards Infectious Diseases.
I must remember and appreciate Dr Michael Gboun, formerly my MPH student,
now UNAIDS Country Director in Sierra Leone. Dr Gboun and his dear wife took
care of me during the periods of my assignments in Botswana. As providence
would have it, he also became a guiding human angel in my sojourn in Kenya and
Somalia.
66
I appreciate the members of the Oke Oko Progressive CDA, Ikorodu and members
of Mbierebe Akpawat Community Organization, Lagos (MACOL) who have
turned up en masse to encourage and support me at this occasion.
Special thanks and appreciation go to the most important set of people in my life;
my Christian brothers and sisters. These are the ones who constantly pray for me in
my trials, in my academic pursuits, in my numerous trips within and outside the
country. These are the ones who encourage me in Christlikeness. I wish to mention
in particular, the national representative of the Bible Standard Ministry, Pastor
W.S. Ebong and his dear wife Senior Deaconess (Sis) Sarah Ebong who have
sacrificed immensely for me seeking my material and eternal welfare. May the
Almighty reward you abundantly in Jesus’ Name.
The elders in the Suru Lere branch of our church, Brothers Efosa Osadolor,
Tommy Nkereuwem, Godfrey Okpugie and Vincent Ogbemudia deserve special
mention for encouraging me as we endeavour to walk in the path of righteousness.
Their constant intercession on my behalf contributed immensely to the success of
this occasion.
It is not always possible to mention everyone who has contributed to one’s
progress in life. In my own case the job becomes more difficult since I have been
blessed with a host of immediate and distant family members and relations all
working in my best interest. My mother was a hard-working business woman who
supported the husband in every aspect and this made it possible for them to train
their children to the best of their abilities. She loved her children to a fault. She
was an epitome of “Sweet Mother”. My mother died from stroke at the tender age
of 62 years.
My father, the late Mr Efiong Ekanem did not obtain any formal education but he
could read and write in the Efik language. His most popular book was the Holy
Bible “Edisana Nwed Abasi Ibom”. He knew the value of western education and
so he sacrificed all his earnings to ensure that his children attain the highest level
of education possible. He passed on at the age of 73 just three months after the
death of his wife. I would have wished he lived a little longer to see me become a
Professor. I truly appreciate his loving care, his constant advice and all the daily
prayers he offered to God on my behalf. My father taught us to trust in God and to
live a life in conformity with His word. I am very proud that today that foundation
has helped me and sustained me even in difficult times.
67
My uncle, Dr Okon Akpan Ekanem, a retired permanent Secretary of Akwa Ibom
State Government, was instrumental to my sojourn in the United States of
America. He was the first in my family to pursue University education in the
United States. He was a pillar of support throughout my stay in the United States.
Now in the absence of my father, he is the head of our immediate family and has
played that role successfully. His wife, Mrs Ene O. Ekanem calls me “My dear”.
She took me up as her child while I was in the U.S and has truly been a dear wife
in the family and a dear mother to me. Thank you mom. May the Almighty
continue to bless you.
Words would fail me in describing the immeasurable love, financial and moral
support I have enjoyed from my distant uncle, Professor Efremfon F. Ekpo,
Professor of Physics at Bethune Cookman College, Daytona Beach, Florida. Prof
Ekpo is my father, my counselor and adviser, and my “Chief of Staff”. You will
live to continue reaping the fruits of your labour. If you have seen me with nice
shirts and ties, you should not marvel the source from which they have been
coming.
My elder sister, Mrs Jemimah Ekefre has played the role of our mother since the
demise of our mother in 1993. My other sisters, Mrs Hannah Okoh, Mrs Ikwo
Joseph Akpan, Mrs Mercy Bassey Udo, and Mrs Affiong Ogbaje are a rare breed
of siblings. I could not have asked God for more. I truly appreciate and love you
all.
God has blessed me with a brother, Engr. Asukwo Ekanem, who despite his
personal challenges in the United States has been there for me financially, morally
and otherwise. God bless you Asu.
I have two special cousins: DSP Imo Effiong of the Nigerian Police Force and Mrs
Etido Mbre of the National Drug Law Enforcement Agency. These two are my
confidants who have stood by me throughout the challenging times of my life. Mrs.
Mbre was the able chair-person of the Inaugural Lecture planning committee from
the home front.
I appreciate the wonderful and supportive role played by my ‘God-sent angels’ –
Grace and Imaobong Ekanem. May God bless and reward you bountifully.
God Almighty has blessed me with beautiful children: beautiful physically,
beautiful morally and beautiful spiritually (by His grace); one daughter and four
sons. What more could I have asked for? I thank them for their understanding and
for helping daddy in various ways.
68
Many other people have contributed I various ways to make this day a success.
They are too numerous to mention. I appreciate you all.
Finally, except the Lord build the house, the labourer laboureth but in vain.
I thank the Almighty God for the strength, for knowledge, for courage, for making
this day possible and for making this occasion a successful one.
Remember:
Epidemiology is the beginning of wisdom in Public Health
but more importantly,
the fear of the Lord is the beginning of true wisdom.
This is my story. This is my song.
Thank you so much for your support and attention.
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