Summary
Zika virus is an arbovirus that is primarily transmitted by the mosquito Aedes aegypti; transmission can also occur transplacentally and sexually. Epidemic outbreaks of Zika virus infection have occurred in South America, US territories, and certain southern US states. Patients often have no or mild flu-like symptoms. However, infection during pregnancy can result in congenital Zika syndrome. Diagnostic confirmation with NAAT is recommended for pregnant patients with a potential Zika virus infection. Treatment is primarily symptomatic, as there is currently no curative therapy.
Epidemiology
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Worldwide geographical distribution [1]
- Outbreaks most commonly occur in tropical and subtropical regions.
- Before 2015, a few cases were reported in Africa, Southeast Asia, and the Pacific islands.
- Since 2015, epidemic outbreaks have been reported in South America (especially Brazil).
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Epidemiology in the US
- Almost all reported cases are acquired during travel to endemic regions. [2]
- During the 2016 outbreak: [3]
- Most locally-acquired cases were reported in US territories (e.g., Puerto Rico).
- Approximately 4000 cases were reported in the continental US, mostly in New York, Florida, California, and Texas.
Epidemiological data refers to the US, unless otherwise specified.
Etiology
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Pathogen: Zika virus
- Genus: flavivirus, type of arbovirus
- Positive-sense, single-stranded, enveloped RNA
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Route of transmission
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Vector-borne transmission by the mosquito Aedes aegypti (common)
- Bite during the daytime
- Can also transmit other infections, e.g., dengue, yellow fever, and chikungunya
- Transplacental transmission from the mother to the fetus
- Sexual transmission
-
Vector-borne transmission by the mosquito Aedes aegypti (common)
References:[4][5]
Clinical features
- Incubation: 2–14 days
- Approx. 80% of cases remain asymptomatic
- In symptomatic patients, the manifestations are usually mild and last for 2–7 days.
- Low-grade fever
- Flu-like symptoms: headache, arthralgia, myalgia, non-purulent conjunctivitis, malaise
- Maculopapular, pruritic rash (20% of cases) [6]
The symptoms of Zika virus infection in adults are usually mild and non-specific, but its complications may be devastating (see “Complications” below).
References:[7]
Diagnosis
General principles [1][2]
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Suspect Zika infection based on symptoms and relevant vector or sexual exposure.
- Within 2 weeks of travel to an area with an outbreak or sexual activity with a person who has recently been in an area with an outbreak [8]
- Up to 12 weeks after symptom onset in a pregnant patient [8]
- Routine lab findings are nonspecific but may include thrombocytopenia and leukopenia. [8]
- Order diagnostic confirmation for patients who are pregnant and have either:
- Clinical features of Zika infection
- A prenatal ultrasound with findings of congenital Zika syndrome
- For patients with vector exposure, exclude dengue infection. [2]
For symptomatic nonpregnant patients who have traveled to an area with an outbreak within the previous 2 weeks, perform only dengue diagnostics; diagnostic testing for Zika virus is not recommended. [2]
Diagnostic confirmation [2]
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NAAT (e.g., RT-PCR) to detect viral RNA
- Recommended for diagnostic confirmation (and to rule out dengue infection)
- Test urine and serum samples simultaneously. [2]
- Testing of other tissues (e.g., placenta, fetus, amniocentesis fluid) may be considered.
-
Serologic testing for Zika virus IgM
- Generally not recommended for diagnosis [2]
- Obtain with Zika virus NAAT for pregnant patients if congenital Zika syndrome is suspected.
- Plaque reduction neutralization test (PRNT): used to confirm the diagnosis in patients with suspected dengue cross-reactivity on serologic testing
Treatment
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Treatment is primarily symptomatic, as there is currently no curative therapy. [1]
- Rest
- IV fluids as needed
- Acetaminophen for fever and/or pain
- Report suspected cases to the health department, even if diagnostic confirmation is not indicated.
- Educate patients about reducing the risk of transmission. See “Prevention” for details.
Zika virus infection is a nationally notifiable disease. [1]
Avoid NSAIDs (e.g., aspirin) until dengue has been ruled out to prevent bleeding. [1]
Complications
- Guillain-Barre syndrome
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Congenital Zika syndrome: growth restriction and significant CNS complications in neonates resulting from intrauterine transmission of the Zika virus
- Microcephaly (craniofacial disproportion)
- Ventriculomegaly
- Subcortical calcifications
- Spasticity (contractures), hyperreflexia, seizures
- Ocular abnormalities (e.g., pigmentary retinal mottling)
- Sensorineural hearing loss
- Miscarriage
References:[7][9]
We list the most important complications. The selection is not exhaustive.
Prevention
- A vaccine against Zika virus does not exist yet.
- Vector control and safer sexual practices are the most important public health measures in endemic regions.
- Individuals traveling to endemic regions should be told to use insect repellents, mosquito nets, and long-sleeved clothing.
- In the case of travel to an endemic region and/or a positive Zika test, couples planning to conceive should use a condom or abstain for the following time periods (even if asymptomatic!):
- During pregnancy
References:[11][12]