GIS ANALYSIS OF LEGIONNAIRE’S DISEASE
IN MICHIGAN
A QUALITATIVE STUDY
BY: James H. Smith
Date: 11/7/13
Class: GIS 4750
Term: Fall 2013
Professor: Dr. Keeger.
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TABLE OF CONTENT
1) ABSTRACT…………………………………………………………………..Pg. 2
2) INTRODUCTION…………………………………………………………..Pg. 2-5
3) RESEARCH QUESTION………………………………………………….Pg. 6
4) HYPOTHESIS………………………………………………………………..Pg. 7
5) LITERARY REVIEW………………………………………………………..Pg. 7-8
6) DATA……………………………………………………………………………Pg. 8
7) METHODOLOGY…………………………………………………………..Pg. 8-10
8) RESULTS……………………………………………………………………….Pg. 10-11
9) CONCLUSION………………………………………………………………..Pg. 11-12
BIBLIOGRAPHY……………………………………………………………...Pg. 12-13
MAP GALLERY……………………………………………………………….Pg. 14-18
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Abstract:
The purpose of this paper is to investigate the incidences of Legionnaire’s
disease in the State of Michigan in 2010. ArcGIS 10.1x will be used to perform
exploratory analysis on the data. Spatial Autocorrelation will be performed using ArcGIS
10.1x, to determine whether or not the incidences are clustered, dispersed or occurred
at random. The results will be displayed as charts, graphs, and maps.
Keywords: Legionnaire’s Disease, Michigan, GIS Analysis, Spatial Auto-Correlation.
Introduction:
Legionnaire’s disease is an infectious disease that affects thousands of
individuals in the U.S. per year. According to the CDC, the bacteria that causes
legionnaire’s disease, occurs naturally in the environment (CDC.gov, 2013).
The bacteria is transmitted to a host, by the inhalation of Water vapor from
cooling towers, and air conditions. A person can also get the disease by swallowing
contaminated water in hot tubs, and swimming pools.
According to the Centers for Disease Control, individuals 50 and over, are the
most at risk of getting the disease. However, the disease can also affect those with
weakened immune systems, chronic lung disease, and cancer.
This makes almost anyone susceptible of getting the disease. The one factor
which makes this disease so lethal, is the fact that its’ symptoms are similar to
Pneumonia. Treating the disease with antibiotics is ineffective, and misdiagnosis is the
leading cause of death.
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Most cases of legionnaire’s disease go unreported, and misdiagnosed as
pneumonia. According to figures gathered by the Center for Disease Control, only 400
cases of legionnaire’s disease were reported in 1990 (CDC.gov, 2013). In 2011, the
prevalence of the disease had increased by 260 percent, to 4200 cases nation-wide
(CDC.gov, 2013). The following chart represents the number of legionnaire cases in the
United States in 2011 by ethnicity.
Figure 1
Source: Center of Disease Control Summary Report
As seen in the chart above, White Americans were affected the most by the disease in
2011, followed by African Americans, and Asian or Pacific Islanders. Native Americans were
affected the least, with only 8 reported cases that year. However, the CDC
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Summary report also indicated that there were 791 incidences of the disease where race was
not reported.
Legionnaire’s Disease in Michigan
In 2010, an outbreak of the disease occurred on a National Guard base in Battle Creek,
Michigan. Six victims were confirmed to have contradicted the disease while on the base in
early July. According to the report, the Army Health Commander ordered the evacuation of the
building where the victims worked. The water in the building was tested for the bacteria that
causes legionnaire’s disease, and subsequently disinfected (Fábregas, Luis and Kilzer).
In late July, 2010; 30 more people at the same facility were suddenly sickened by a
bacteria outbreak (Fábregas, Luis and Kilzer). The most recent outbreak occurred in June of
2013. According to a news report, a family of 24 from Saginaw, MI. got sick after visiting a
resort in Boyne City, Michigan (RSOE EDIS). Seven of the family members were hospitalized;
two of them were in critical condition.
The chart in figure 2. Show the total number of legionnaire cases for the past five years
in the State of Michigan.
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Figure 2
Source: Center for Disease Control, 2013
As seen in the chart above, the prevalence of legionnaire’s disease in the State of
Michigan, increased 40 percent since 2009. Although the total number of confirmed cases are
small, compared to other contagious diseases in the State; the increase indicates a growing
problem in the detection and prevention of the disease throughout the state.
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Research Question:
The purpose of this study is to utilize GIS technology to investigate the prevalence of
Legionnaire’s disease in the State of Michigan. It will attempt to answer the following
questions:
1).
is the distribution of legionnaire cases clustered?
2).
is the distribution of Legionnaire’s disease dispersed?
3).
is the distribution of Legionnaire’s Disease the result of a random occurrence?
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The map below show the distribution of Legionnaire cases to date, in 2013.
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Source: Michigan Geographic Library, 2013
As seen in the map above, there is a concentration of confirmed cases in the
southeastern portion of the Lower Peninsula. Statistical analysis will be performed on the data
to determine if the pattern is significantly dispersed or clustered.
Hypothesis:
Based on the map above, my hypothesis is the following:
A).
H₁ = the distribution of Legionnaire’s disease is significantly clustered.
B).
H₀ = the distribution of Legionnaire’s disease is the result of random occurrences.
The null hypothesis is accepted if the p-value is greater than five percent. The null hypothesis, (H₀), is
rejected if the p-value is five percent or less.
Literary Review
There have been numerous studies concerning Legionnaire’s disease throughout the
world. The following is a sample of the most relevant studies:
1)
(Loughlin et al. 2007), Performed a study on the incidence of legionella bacteria in a restaurant in
Rapid City, South Dakota. The research group collected both environmental, and social data of
people testing positive for the disease. The results of the analysis was compared with the analysis of
the control group. The analysis indicated that there was a significantly greater chance that the
infected individuals traveled through areas contaminated with the bacteria which causes
legionnaire’s disease.
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2)
The environmental protection agency, performed a study which investigated the risks that
Legionnaire’s disease pose to children. The report stated that children are more susceptible to
diseases, because their immune system is still developing (Epa and Ost 1999).
3)
(Infuso et al. 1997), performed a study which investigated the outbreak of legionnaire’s disease in
southwest France. The outbreak occurred in 1996, during a camping trip consisting of 42 Dutch
tourist. Two of the campers were reported to have contracted Legionnaire’s disease.
4)
The studies above are relevant because they show that the disease can affect anyone, no matter
where you live. My study is relevant, because there is a need for GIS analysis to be performed on the
distribution of legionnaire cases in the State of Michigan.
Data
The data collected for this study include the following:
1).
Michigan County Shape file:
This file was obtained from the Michigan Geographic Library. The
shape file is a 1: 24,000 representation of counties in Michigan. The attached database table has data on the name,
area, county code, and geometry of each county in the state of Michigan.
2).
Legionnaire Disease confirmed cases: Data on the number of confirmed cases of legionnaire’s
disease in the state of Michigan, was obtained from the Michigan Department of Community Health’s weekly
surveillance report. The data gathered was from January 2013 through November 1, 2013. The data was placed in
an excel spreadsheet, and joined to the county shape file’s attribute table.
Methodology:
In order to determine whether or not the distribution of cases were dispersed, I chose
to use Spatial Autocorrelation. Spatial Autocorrelation is a tool in ESRI Arc Toolbox, which
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determines the global spread or clustering of data in the distribution. The formula for Moran’s I
spatial autocorrelation index is displayed below:
Source: ESRI ArcGIS Tutorial.
The index value for the Global Moran I is determined by calculating the variance and
mean of neighboring features. The standard deviation of these neighbors are multiplied
together, and the product is multiplied by the total number of features. The subsequent value
is then divided by the product of the aggregate weights, and the sum of the deviations squared
(ESRI ArcGIS 10.1 tutorial, 2013).
Moran I also calculates the P value, and Z score for the distribution. Based on the two
values, the significance of the distribution can be determined. (ESRI ArcGIS 10.1 tutorial).
Below is a chart which explains the potential outcome of the Moran I analysis, and rules on
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Accepting or rejecting the null hypothesis.
Figure 3
Source: Arc GIS 10.1 Help
Results
The result of the Moran I analysis is displayed in the graphic image below.
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Figure 4
The z-score for the data is 8.42. A high positive z-score indicates the presence of a
global clustered pattern. The low p-value indicates that the pattern is statistically significant;
therefore the null hypothesis is rejected.
Conclusion
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Based on the analysis of the data, there is a need to further investigate the continued
presence of Legionnaire’s disease in the state. Special attention should be given to those
cluster of counties where outbreaks of legionnaire’s disease have been prominent.
In addition to investigating the presence of the disease in those counties, there is a
need to educate the public about the disease. As stated in the introduction, misdiagnosis is the
leading cause of death from the disease. If the public is aware of the symptoms, and cause of
the disease; they can better protect themselves from becoming infected. GIS technology is a
valuable tool that can be used in the analysis, and tracking of the disease in the state.
This study could be improved by obtaining data at the census tract level, instead of the
county level. Analyzing data collected at a higher scale, would be beneficial in helping to
identify neighborhoods that were affected the most by this disease.
Bibliography
WWW.ESRI.com, ArcGIS 10.1 Spatial Auto-Correlation tutorial.
Epa, U S, and O W Ost. 1999. “Legionella : Risk for Infants and Children” (November).
Fábregas, Luis and Kilzer, Lou. “Unreported and Misunderstood, Legionnaire Cases Across the
U.S. Soar.” http://triblive.com/news/allegheny/3725123-74/legionnaires-cases-disease.
Infuso, A, B Hubert, D Dumas, M Reyrolle, S De Mateo, C Pelaz, C Hemery, and I Perez. 1997.
“Outbreak of Legionnaire s Disease in Two Groups of Tourists Staying at Camp Sites in
France.” Euro Surveillance : Bulletin Europeen Sur Les Maladies Transmissibles = European
Communicable Disease Bulletin 2: 48–50.
http://www.ncbi.nlm.nih.gov/pubmed/12631812.
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Loughlin, Rosalyn E O, Lon Kightlinger, Matthew C Werpy, Ellen Brown, Valerie Stevens, Clark
Hepper, Tim Keane, et al. 2007. “Restaurant Outbreak of Legionnaires ’ Disease Associated
with a Decorative Fountain : an Environmental and Case-Control Study” 24: 1–9.
doi:10.1186/1471-2334-7-93.
RSOE EDIS. “Epidemic Hazards in USA.”
http://hisz.rsoe.hu/alertmap/site/?pageid=event_desc&edis_id=EH-20120626-35560-USA.
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Map Gallery
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