page_title: Zika fever
section_title: Epidemiology
hierarchical_section_title: Zika fever / Epidemiology
caption_attribution_description: English: US CDC map of all countries with active Zika virus transmission in September 2016
context_page_description: Zika fever, also known as Zika virus disease or simply Zika, is an infectious disease caused by the Zika virus. Most cases have no symptoms, but when present they are usually mild and can resemble dengue fever. Symptoms may include fever, red eyes, joint pain, headache, and a maculopapular rash. Symptoms generally last less than seven days. It has not caused any reported deaths during the initial infection. Mother-to-child transmission during pregnancy can cause microcephaly and other brain malformations in some babies. Infections in adults have been linked to Guillain–Barré syndrome.
  Zika fever is mainly spread via the bite of mosquitoes of the Aedes type. It can also be sexually transmitted and potentially spread by blood transfusions. Infections in pregnant women can spread to the baby. Diagnosis is by testing the blood, urine, or saliva for the presence of the virus's RNA when the person is sick, or the blood for antibodies after symptoms are present more than a week.
  Prevention involves decreasing mosquito bites in areas where the disease occurs and proper use of condoms.
context_section_description: In April 1947, as part of studies sponsored by the Rockefeller Foundation into yellow fever, 6 caged rhesus monkeys were placed in the canopy of the Zika Forest of Uganda. On April 18 one of the monkeys (no. 776) developed a fever and blood samples revealed the first known case of Zika fever. Population surveys at the time in Uganda found 6.1% of individuals to be seropositive for Zika. The first human cases were reported in Nigeria in 1954. A few outbreaks have been reported in tropical Africa and in some areas in Southeast Asia. There have been no documented cases of Zika virus in the Indian subcontinent. Surveys have found antibodies to Zika in healthy people in India which could indicate past exposure, though it could also be due to cross-reaction with other flaviviruses.
  By using phylogenetic analysis of Asian strains, it was estimated that Zika virus had moved to Southeast Asia by 1945. In 1977–1978, Zika virus infection was described as a cause of fever in Indonesia. Before 2007, there were only 13 reported natural infections with Zika virus, all with a mild, self-limited febrile illness.
caption: Countries with active Zika virus transmission as of September 2016.
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