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For further information, see CMDT Part 32-05: Other Systemic Viral Diseases

Key Features

Essentials of Diagnosis

  • Most infected persons asymptomatically seroconvert

  • Clinical symptoms are akin to those of chikungunya virus infection but with less arthritis

  • Complications include microcephaly and ocular complications in infants born to mothers infected during pregnancy; as well as Guillain-Barré syndrome in adults

  • No effective antiviral or vaccine is available

General Considerations

  • Zika virus is a flavivirus, akin to the viruses that cause dengue fever, Japanese encephalitis, and West Nile infection

  • Aedes species mosquitoes, particularly Aedes aegypti, are responsible for transmission of Zika virus

  • The biodistribution of the Aedes species mosquitoes largely determines the area of prevalence for Zika virus

  • Aedes species mosquitoes are found primarily in the southeastern United States, but one species, Aedes albopictus (the Asian tiger mosquito, known to sequester in standing water, eg in tires), may be found as far north as Pennsylvania

  • Modes of Zika virus transmission

    • Sexual: reported from males and females to partners via vaginal, anal, or oral sex

    • Vertical: reported from pregnant woman to fetus

    • Transfusion: reported from platelet transfusion

  • Demographics

    • The Zika virus was first noted in Africa and Asia during the 1950s–1980s

    • A large outbreak occurred in French Polynesia in 2013

  • A smaller outbreak occurred on Easter Island during 2014

  • An outbreak began in northeastern Brazil in 2015; 239,742 cases were subsequently reported between 2015 and 2018

  • The CDC case count for the year 2021, as of November 2, 2021, includes 1 case (a returning traveler) in the US states and 25 cases (all locally acquired) in the US territories

Clinical Findings

Symptoms and Signs

  • Incubation period is 3–14 days

  • Most infections are asymptomatic

  • Acute onset fever

  • Maculopapular rash, often pruritic; rash may outlast the fever but is not always present

  • Nonpurulent conjunctivitis

  • Arthralgias

  • Rash may outlast the fever but is not always present

  • Symptoms last up to 7 days

Differential Diagnosis

  • Dengue

  • Chikungunya virus infection


  • The CDC recommends that everyone with symptoms of Zika infection be tested if they have traveled to an endemic area with active transmission as well as all pregnant women who have lived in or visited affected regions

  • Diagnosis is made by detecting viral RNA or neutralizing antibody, IgM 4 days or more after symptom onset or IgG after 7 days or more

  • Reverse transcriptase polymerase chain reaction (RT-PCR) detects the virus in blood or urine and should be performed within 2 weeks of illness onset

  • Matched serum and urine specimens should be tested simultaneously


  • No antivirals are approved to treat Zika virus

  • Sofosbuvir

    • Shows some ability to inhibit Zika replication and infection in vitro

    • Appears to be ...

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