Zika Virus

updated Oct. 3, 2016


Zika virus (ZIKV) is a mosquito-borne RNA flavivirus.

  • The flavivirus genus includes multiple other human viral infections, including yellow fever, West Nile, dengue and tick-borne encephalitis.
  • The primary vector for Zika virus is Aedes aegypti, though Aedes albopictus can also transmit it.

While outbreaks have been previously reported in Africa, Asia and the islands of the Pacific, it was first reported in the Western Hemisphere in May 2015 in Brazil.

  • Per the CDC, as of August 3, 2016, local mosquito-borne transmission had been identified in at least 42 countries or territories in the Americas. (
  • There has been limited local mosquito-borne transmission in the Continental US. This remains an evolving problem with ongoing concern that endemic Zika transmission may develop in the Southeastern US.
  • As of August 3, 2016, there have been 1,658 travel-related Zika cases reported in the US, with 433 pregnant women in the US demonstrating laboratory evidence of Zika (
  • Zike virus can be spread through sexual contact, including male-to-female and male-to-male contact.
  • There have been reports of possible person-to-person transmission through blood transfusion, but none in the US. (
  • The World Health Organization has designated the Zika virus as a public health emergency of international concern

Clinical Disease

  • One in five infected become symptomatic
  • Clinical illness is usually mild and lasts for several days or a week
    • Severe disease is uncommon, though Guillain-Barre syndrome has been reported in patients following suspected Zika infection
    • Fatalities are rare
    • Of note: Zika virus can cause fetal microcephaly and other severe fetal brain defects. The CDC is recommending travel precautions for pregnant women or women who may become pregnant potentially traveling to Zika endemic areas. (
  • Characteristic clinical findings can include:
    • acute onset of fever,
    • maculopapular rash (Zika patient photo, right),
    • arthralgia,
    • conjunctivitis

Diagnosis and Treatment

  • Consider the diagnosis in symptomatic travelers returning from affected areas
  • RT-PCR can be used on serum specimens from the first week of illness which can be performed by the CDC Division of Vector-Borne Diseases and many state health departments (contact your state or local health department for more information). The MAC-ELISA test is also available from the CDC and many state health departments. This test detects IgM antibodies and can be used for testing symptomatic patients >14 days after symptom onset and asymptomatic pregnant women who traveled to an area with Zika virus transmission in the previous two to 12 weeks.
  • RT-PCR testing is also available from commercial laboratories.
  • Treatment is symptomatic and supportive
    • No specific antiviral therapy is available
  • The CDC and ACOG have developed guidelines of the evaluation of pregnant women who have traveled to Zika-endemic area (see below).


  • There is no current vaccine or antiviral available to prevent Zika infection
  • Avoid mosquito bites
    • Wear long sleeves and pants
    • Use insect repellents when outdoors (such as DEET)
  • Delay travel to known affected areas if you are pregnant or attempting to become pregnant
  • Consider use of contraceptive measures (condoms) if traveling to known affected areas and upon return of the individual or their sexual partner.


Update: Interim Guidance for Preconception Counseling and Prevention of Sexual Transmission of Zika Virus for Persons with Possible Zika Virus Exposure — United States, September 2016 CDC Morbidity and Mortality Weekly Report (MMWR)

Zika Virus: Critical Information for Emergency Providers - July 2016

Quarantine for Zika Virus? Where is the Science? - April 2016

Identify-Isolate-Inform: A tool for initial detection and management of Zika virus patients in the emergency department - April 2016

US CDC Zika Virus - Current, up-to-date information and recommendations.
CDC Health Advisory - Jan. 15, 2016


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