Zika Virus

Reviewed 06/2017

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Subject: Zika Virus

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  • Zika virus is a single-stranded RNA virus (family Flaviviridae).

  • Transmitted by Aedes spp. mosquitoes (especially Aedes aegypti) which also transmit dengue and chikungunya

  • Incubation estimated to be several days to a week

  • 80% of infections are asymptomatic.

  • Symptomatic illness: acute onset of fever, maculopapular rash, joint pain, and/or conjunctivitis

  • Generally mild; symptoms: several days to a week

  • Zika virus infection in pregnant women might lead to microcephaly in offspring (please see “Pregnancy Considerations”); a link to Guillain-Barré syndrome (GBS) is possible.


  • 1950s: sporadic human cases in Africa and Southeast Asia

  • 2007: outbreak of Zika virus in Yap island, Micronesia (1)

  • 2013 to 2014: French Polynesia, >28,000 suspected Zika virus infections

  • 2015: Zika virus outbreak in Brazil, >50,000 cases

  • Currently : Zika virus transmission in Central America, tropical South America and the Caribbean, Marshall Island, Tonga, Thailand, Indonesia, and Cape Verde

  • As of March 2, 2016, no vector-borne cases acquired in the continental United States; probable sexually acquired case reported. Travel-associated Zika virus infections are reported worldwide.


  • Bites of Aedes spp. especially A. aegypti mosquitoes

  • Aggressive daytime feeders; bites can also occur at night.

  • Other modes of transmission: maternal–fetal (intrauterine, perinatal); transfusion (2); sexual (3)

  • Neurotropic in animals; can cause neural cell death

Pregnancy Considerations

  • Pregnant women do not have more severe disease or increased susceptibility; however, the developing fetus could be at risk for microcephaly and other congenital abnormalities (4).

  • Pregnant women who have traveled to an area with ongoing Zika virus transmission should have Zika IgM antibody measured 2 to 12 weeks postexposure to detect infection, even if asymptomatic (4).

  • Pregnant women with an illness consistent with Zika virus disease during or within 2 weeks of exposure, reverse-transcriptase-polymerase chain reaction (RT-PCR) (<7 days after symptoms onset) of maternal serum, or Zika IgM (>4 days after onset of symptoms). Additional tests may be needed to rule out cross-reactive antibodies (4).

  • Pregnant women with Zika virus infection should be evaluated by a specialist (4).

  • Amniocentesis and ultrasounds may be recommended to assess for fetal infection and/or congenital malformation (4).

  • BREASTFEEDING for mothers with Zika virus infection

    • Zika virus RNA has been identified in breast milk.

    • No cases of Zika transmission associated with breastfeeding have been reported (5).

    • Current evidence suggests benefits of breastfeeding outweigh theoretical risks to infants.



People living in, or traveling to, an endemic area not previously infected. Immunity will likely develop after initial infection. 


  • No vaccine or antiviral therapy is currently available.

  • Prevention via insect repellents/mosquito control and clothing that minimizes skin exposure, especially during daylight hours.

  • Pregnant women should consider avoiding travel to areas with ongoing Zika virus outbreaks.

  • Male partners exposed to, or infected with, Zika virus should use condoms correctly and consistently or refrain from sex with pregnant women.



  • 20% of person infected with Zika virus develop symptoms.

  • Fever, myalgia, joint pain, conjunctivitis, retro-ocular pain, and maculopapular rash are common symptoms (two or more usually present), self-limited in most instances.

  • Incubation period is not well understood but likely short.

  • Severe disease requiring hospital admission is uncommon; mortality is very rare.

  • Travel history to area with outbreak


  • Exam findings nonspecific and overlap with other viral infections (dengue can cocirculate)

  • Maculopapular rash can be local or diffuse.

  • Conjunctivitis


  • Dengue

  • Chikungunya

  • Malaria

  • Rickettsia

  • Leptospirosis

  • Enterovirus, adenovirus, parvovirus

  • Group A Streptococcus

  • Rubella, measles


  • The FDA has issued an emergency use authorization for the CDC’s Zika virus ELISA for qualified labs.

  • Testing in the United States should be done in consultation with state health departments.

  • RT-PCR (6)

    • Should be done within 7 days after symptom onset

    • Sensitivity of RT-PCR is high due to high-level viremia.

  • Serology for Zika virus–specific IgM (ELISA)

    • Sample should be obtained at least 4 days after symptom onset.

    • IgM antibodies present at least 2 weeks after exposure; persist for at least 12 weeks.

    • Cross-reactivity with other Flaviviruses such as dengue and yellow fever viruses can generate false-positive result, as can previous vaccination with Japanese encephalitis virus vaccine.

  • Serum and/or cerebrospinal fluid can be sent to CDC for RT-PCR, serology, and viral isolation.

  • Other body fluids (urine, amniotic fluid, semen, saliva) can be tested for RT-PCR and viral isolation.



  • Usually mild and self-limited infection. Treatment is supportive.

  • Aspirin or other NSAID use should be avoided if dengue infection is possible.

  • Persons with Zika virus infection should use insect repellent to avoid additional bites, as this can lead to person-vector-person spread.


  • Increases in GBS have been reported in areas with Zika virus transmission and a link is possible (7).

  • Twenty-fold increase in microcephaly in infants, and other congenital malformations were observed with Zika virus infection in Brazil, although causality has not been definitively determined (8,9).


  • Zika virus disease is a nationally notifiable disease, and health care providers encouraged to report suspected cases to their state health department.

  • Lab-confirmed cases should be reported to CDC to assess and reduce the risk of local transmission to prevent further spread of the disease.


Duffy MR, Chen TH, Hancock WT et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med.  2009;360(24):2536–2543.  [View Abstract]
Musso D, Nhan T, Robin E et al. Potential for Zika virus transmission through blood transfusion demonstrated during an outbreak in French Polynesia, November 2013 to February 2014. Euro Surveill.  2014;19(14).  [View Abstract]
Hills SL, Russell K, Hennessey M et al. Transmission of Zika virus through sexual contact with travelers to areas of ongoing transmission—Continental United States, 2016. MMWR Morb Mortal Wkly Rep.  2016;65(8):215–216.  [View Abstract]
Fleming-Dutra KE, Nelson JM, Fischer M et al. Update: interim guidelines for health care providers caring for infants and children with possible Zika virus infection—United States, February 2016. MMWR Morb Mortal Wkly Rep.  2016;65(7):182–187.  [View Abstract]
Chan JF, Choi GK, Yip CC et al. Zika fever and congenital Zika syndrome: an unexpected emerging arboviral disease. J Infect.  2016;72(5):507–524.  [View Abstract]
Faye O, Faye O, Diallo D et al. Quantitative real-time PCR detection of Zika virus and evaluation with field-caught mosquitoes. Virol J.  2013;10:311.  [View Abstract]
Oehler E, Watrin L, Larre P et al. Zika virus infection complicated by Guillain-Barre syndrome—case report, French Polynesia, December 2013. Euro Surveill.  2014;19(9).  [View Abstract]
Brasil P, Pereira JP Jr, Raja Gabaglia C et al. Zika virus infection in pregnant women in Rio de Janeiro. N Engl J Med.  2016;375(24):2321–2334.  [View Abstract]
Heukelbach J, Alencar CH, Kelvin AA et al. Zika virus outbreak in Brazil. J Infect Dev Ctries.  2016;10(2):116–120.  [View Abstract]


  • Meaney-Delman D, Hills SL, Williams C et al. Zika virus infection among U.S. pregnant travelers—August 2015-February 2016. MMWR Morb Mortal Wkly Rep.  2016;65(8):211–214.  [View Abstract]

  • Oduyebo T, Petersen EE, Rasmussen SA et al. Update: interim guidelines for health care providers caring for pregnant women and women of reproductive age with possible Zika virus exposure—United States, 2016. MMWR Morb Mortal Wkly Rep.  2016;65(5):122–127.  [View Abstract]

  • Schuler-Faccini L, Ribeiro EM, Feitosa IM et al. Possible association between Zika virus infection and microcephaly—Brazil, 2015. MMWR Morb Mortal Wkly Rep.  2016;65(3):59–62.  [View Abstract]



A92.8 Other specified mosquito-borne viral fevers 


066.3 Other mosquito-borne fever 


3928002 Zika virus disease (disorder) 


  • Clinical illness is generally mild and self-limited; most infections are asymptomatic.

  • Dengue virus can be cocirculating and the clinical presentation can be similar; testing to distinguish between the two is suggested.

  • Although definitive evidence is lacking, Zika virus is strongly linked to microcephaly in infants infected in utero and GBS.

  • Infection appears to induce host immunity.