ZIKA VIRUS UPDATE
April 25, 2016
What is Zika virus?
• Single-stranded,
enveloped RNA virus
• In the Flaviviridae
family
• Yellow fever
• West Nile
• Dengue
• St. Louis encephalitis
A transmission electron micrograph of the Zika virus (CDC)
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History of Zika virus
• First discovered in rhesus monkeys 1947 in Uganda, near
the Zika Forest
• Subsequently described in humans in 1952 in Uganda and
United Republic of Tanzania
• Cases in Africa and Asia during 20th century
• First outbreak outside of Asia or Africa in 2007 in Yap
(Federated States of Micronesia)
• Outbreak in French Polynesia in October 2013
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Recent History of Zika virus
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Transmission
• Primarily through the bite of an infected Aedes sp.
mosquito
• Same mosquitoes that spread dengue, chikungunya, and
yellow fever
• Typically lay eggs in containers and standing water
• Aggressive daytime biters, can also bite at night
• Prefer to bite people
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Aedes aegypti and Aedes albopictus
Aedes aegypti
Aedes albopictus
(Asian tiger mosquito)
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Primary vectors
Ae. aegypti
Ae. albopictus
• Strong preference for human blood
• Indiscriminate feeder
• Lives around human habitations in
• Lives near human habitations in
urban areas
• Lays eggs and produces larvae
preferentially in artificial containers
• Primarily daytime feeder; rests
indoors
• High vectorial capacity for Zika
(effectiveness of virus transmission
in nature)
suburban/rural areas
• Lays eggs and produces larvae in
natural or artificial containers
• Aggressive, daytime feeder in
outdoor areas
• Competent vector of Zika
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Life cycle of Aedes mosquito
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Updated Aedes Distribution Maps, March 30, 2016
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Other modes of transmission
• From mother to child
• During pregnancy or delivery from a mother already infected
• To date, no reports of infants getting Zika virus through
breastfeeding
• Through infected blood or sexual contact
• Spread of the virus through blood transfusion and sexual contact
has been reported
• Through organ or tissue donation
• No confirmed cases but theoretically possible
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Sexual transmission: what we know
• Zika virus can be spread by a man to his sex partners
• In known cases of likely sexual transmission, the men had
Zika symptoms
• Virus can be spread before, during, and after men have
symptoms
• The virus can be present in semen longer than in blood
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Suggested timeframes to wait before trying to
get pregnant
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Incubation Period and Symptoms
• Incubation period not known
• Likely few days to 2 weeks
• Most infections are asymptomatic
• Most common symptoms
• Fever
• Rash – very common, often itchy
• Joint pain
• Conjunctivitis (red eyes)
• Other symptoms include muscle pain and headache
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Clinical Presentation
Fever
Rash
Conjunctivitis
Arthralgia
Myalgia
Headache
Hemorrhage
Shock
Zika
++
+++
++
++
+
+
-
Dengue
+++
+
+
++
++
++
+
Chikungunya
+++
++
+++
+
++
-
*Courtesy Dr. Ingrid Rabe, CDC
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Zika & pregnancy
• Increased rates of microcephaly
noted in Brazil in late 2015
• 10-20x normal (reported)
incidence
• Prior associations with
neurological and auto-immune
complications in French
Polynesia outbreak
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April 13, 2016
On the basis of this review, we conclude that a causal
relationship exists between prenatal Zika virus infection
and microcephaly and other serious brain anomalies.
Diagnostic Testing
• PCR can detect virus in first week after illness onset
• Serological testing can detect illness for longer
• IgM detectable starting ~day #4 after illness onset
• Potential cross-reactivity with other viruses (WNV, YFV, Dengue) making
test interpretation sometimes difficult
• More complex serological tests can be done to help distinguish Zika from
other infections; less helpful if previously infected/vaccinated
• PCR and IgM ELISA now available at DHMH public health
laboratory; CDC conducts confirmatory testing
• No commercial testing available at this time
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Treatment
• No specific antiviral treatment
• No vaccine
• Supportive — rest, fluids, antipyretics, anti-nausea meds
• Acetaminophen for fever and pain
• Avoid aspirin and NSAIDS until dengue ruled out to avoid
hemorrhagic complications
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When providers want to test patients for Zika
LHD, DHMH personnel can approve testing at DHMH Labs for:
• Asymptomatic pregnant women with travel history to Zika-affected
area during pregnancy or who become pregnant within 2 weeks of
travel
• Symptomatic travelers (male and female)
• With 1 or more major symptoms (fever, rash, conjunctivitis, arthralgia), AND
• Symptom onset within 2 weeks of last day in Zika-affected country
• Pregnant partners of recent travelers to Zika-affected areas
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Countries and territories with active Zika virus transmission
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U.S. Zika virus cases, as of April 20, 2016
Lab-confirmed Zika virus
disease cases, reported to
ArboNet in US States, as of
April 20, 2016
• Travel-associated Zika
virus disease cases
reported: 388
• Locally acquired vectorborne cases reported: 0
• Total: 388
• Pregnant: 33
• Sexually transmitted: 8
• Guillain-Barre syndrome: 1
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Maryland confirmed Zika virus infections
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Threat to Maryland
• No locally acquired mosquito-borne Zika virus disease cases have
been reported in the continental US but there have been locally
acquired cases in Puerto Rico, the US Virgin Islands, and other
U.S. territories
• Many travel-associated Zika cases identified in the U.S. and will
continue to increase
• Many infections will not be diagnosed but could potentially serve as
source for transmission
• Travel-associated cases could result in local spread of the virus in
the U.S., including in Maryland
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Air travel between U.S. and Zika affected areas
• ~30 million people fly to the U.S. each
year from countries in the Caribbean
and Latin America1
• Unlikely Zika would spread as quickly or
as widely in the U.S.2
• Better public health infrastructure
• More air conditioning and screening
• Earlier disease detection
• Better mosquito control
1. Sources: Bureau of Transportation Statistics (air travel data)
2. “Anticipating the international spread of Zika virus from Brazil,” The Lancet. Isaac I. Bogoch and Kamran Khan, University of Toronto; Oliver J. Brady and Moritz U.G. Kraemer,
University of Oxford
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Maryland Public Health Response
• Providing Zika information to Marylanders via a variety of formats (including
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website and social media)
Providing guidance to MD healthcare providers
Working with providers for Zika testing at DHMH (with focus on pregnant
women)
Coordinating medical management for Zika-infected pregnant women and
infants
Conducting surveillance and epidemiologic investigations
• Zika infection (reportable)
• Microcephaly (reportable, including by hospitals)
• GBS
• Mosquito
• Controlling mosquitoes (in concert with MD Dept of Agriculture)
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Current Statewide Zika Activities
• Zika Awareness Week (April 24-30)
• Governor proclamations to all LHDs
• LHDs asked to host/sponsor Zika-related
activities
• Zika Prevention Kits for pregnant
women
• Educational information
• Repellent
• Larvicide
• Condoms
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Vector Control for Zika Virus ≠
Vector Control for West Nile Virus
• Whereas mosquito-based surveillance is the preferred
method for monitoring or predicting West Nile virus
outbreaks, it is not the preferred method for monitoring or
predicting Zika (dengue, chikungunya, or yellow fever)
outbreaks
• For these arboviruses, it is more efficient to detect cases in
people
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Aedes Surveillance and Control
• Surveillance
• Determine presence or absence of Aedes
• Identify types of containers are producing the most mosquitoes for targeting
vector control efforts
• Understand where mosquito populations occur
• Monitor the effectiveness of vector control efforts
• Control
• Community and property clean up
• Application of larvicide
• Application of adulticide
• Education about personal protection
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Principal functions of Zika, dengue and chikungunya
mosquito-based surveillance programs
• Determine presence or absence of Ae. aegypti and Ae. albopictus in a
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•
geographic area
Identify what types of containers are producing the most mosquitoes for
targeting vector control efforts
Track larval sites if Ae. aegypti or Ae. albopictus are detected in an area
Collect mosquito population data and identify geographic areas of high
abundance (high-risk)
Monitor the effectiveness of vector control efforts
Collect data on mosquito infection rates during outbreaks to:
• identify primary/secondary mosquito vectors
• establish thresholds at which humans get infected
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Focused vector control activities when any of the
following occurs:
a) Any detection of Ae. aegypti;
b) Threshold levels of Ae. albopictus are reached; OR
c) Travel-associated cases of Zika virus infection are detected
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Mosquito Bite Prevention
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Aedes albopictus