Symptoms and causes

Symptoms

The mosquito that carries Zika virus is found worldwide.

Stay up-to-date on virus disease cases on the CDC's Zika virus disease website.

As many as four out of five people infected with Zika virus have no signs or symptoms. When symptoms do occur, they usually begin two to seven days after being bitten by an infected mosquito. Signs and symptoms of Zika virus disease most commonly include:

  • mild fever
  • rash
  • joint or muscle pain

Other signs and symptoms may include:

  • headache
  • red eyes (conjunctivitis)

Most people recover fully, with symptoms resolving in about a week.

When to see a doctor

See your doctor if you think you or a family member may have Zika virus, especially if you have recently traveled to an area where there's an ongoing outbreak. The Centers for Disease Control and Prevention (CDC) has blood tests to look for Zika virus or similar diseases such as dengue or chikungunya viruses, which are spread by the same type of mosquitoes.

Causes

Zika virus is transmitted primarily through the bite of an infected Aedes species mosquito, which is found throughout the world. It was first identified in the Zika Valley in Africa in 1947, but outbreaks have since been reported in southeastern and southern Asia, the Pacific Islands and the Americas.

When a mosquito bites a person infected with a Zika virus, the virus enters the mosquito. When the infected mosquito then bites another person, the virus enters that person's bloodstream.

Spread of the virus through sexual contact and blood transfusion have been reported.

Risk factors

Factors that put you at greater risk of developing Zika virus disease include:

  • Living or traveling in areas where there have been outbreaks. Being in tropical and subtropical areas increases your risk of exposure to the virus that causes Zika virus disease. Especially high-risk areas include several islands of the Pacific region, a number of countries in Central, South and North America, and islands near West Africa. Because the mosquito that carries Zika virus is found worldwide, it's likely that outbreaks will continue to spread to new regions.

    The mosquitoes that carry Zika virus are found in some parts of the United States, including Puerto Rico and South Florida.

  • Having unprotected sex. Isolated cases of sexually transmitted Zika virus have been reported. The CDC advises abstinence from sexual activity during pregnancy or condom use during all sexual contact for men with a pregnant sex partner if the man has traveled to an area of active Zika virus transmission.

Complications

Zika virus infections during pregnancy have been linked to miscarriage and microcephaly, a potentially fatal congenital brain condition. Zika virus also may cause other neurological disorders such as Guillain-Barre syndrome.

Aug. 23, 2017
References
  1. AskMayoExpert. Zika. Rochester, Minn.: Mayo Foundation for Medical Education and Research; 2016.
  2. Schuler-Faccini L, et al. Possible association between Zika virus infection and microcephaly – Brazil, 2015. The Morbidity and Mortality Weekly Report. 2016;65:59.
  3. Ayres CFJ. Identification of Zika virus vectors and implications for control. The Lancet. In press. Accessed Feb. 12, 2016.
  4. Zika virus. The Centers for Disease Control and Prevention. http://www.cdc.gov/zika/index.html. Accessed Feb. 12, 2016.
  5. Recommendations for donor screening, deferral, and product management to reduce the risk of transfusion-transmission of Zika virus. U.S. Food and Drug Administration. http://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/Blood/UCM486360.pdf?elq_cid=1276914&x_id=&elqTrackId=3c05e939c7654e97b748609b4507885e&elq=e87e12610c974fa0a1191639391fedae&elqaid=49412&elqat=1&elqCampaignId=21484. Accessed Feb. 18, 2016.
  6. Rasmussen SA, et al. Zika virus and birth defects – Reviewing the evidence for causality. New England Journal of Medicine. http://www.nejm.org. Accessed April 15, 2016.