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Zika Virus

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Zika virus facts

  • Zika virus is a virus related to dengue, West Nile, and other viruses.
  • Zika virus may play a role in developing congenital microcephaly (small head and brain) in the fetus of infected pregnant women.
  • The viral disease was first noted in 1947 in Africa and has spread by outbreaks to many different countries, with an ongoing outbreak in Brazil and Puerto Rico; the first diagnosis of Zika virus in the U.S. occurred in Harris County (Houston), Texas, in January 2016.
  • The virus is transmitted to most people by a mosquito (Aedes) vector; the risk factor for infection is a mosquito bite.
  • The Zika virus' incubation period is about three to 12 days after the bite of an infected mosquito.
  • The vast majority of infections are not contagious from person to person; however, it may be passed person to person during sex.
  • The Zika virus symptoms and signs are usually
  • The virus infection is usually diagnosed by the patient's history and physical exam and by blood testing (testing for the virus genome; usually done in the United States by the Centers for Disease Control and Prevention [CDC]).
  • Treatment is related to symptom control, and over-the-counter medication is used in most infected people.
  • Rarely, complications such as dehydration or neurologic problems may develop.
  • In Brazil, an outbreak of Zika virus infections may be related to the development of congenital microcephaly; evidence comes from epidemiology and from Zika viruses isolated from amniotic fluid and the brain and heart of an infant with microcephaly.
  • The prognosis for most Zika virus infections is good; however, complications such as microcephaly, if proven to be related to the infection in pregnancy, would be a poor outcome for the newborn. In addition, eye abnormalities, Guillain-Barré syndrome, and acute disseminated encephalomyelitis (ADEM) may occur, with fair to poor outcomes.
  • Prevention of Zika virus infections is possible if mosquito bites from infected mosquitoes are prevented.
  • Currently, there is no vaccine against Zika virus infection; however, the possible link to development of microcephaly in the fetus has prompted physicians to lobby for a fast development of a vaccine.
Picture of an Aedes aegypti mosquito, the vector that transmits the Zika virus
Picture of an Aedes aegypti mosquito, a vector that transmits the Zika virus; Photo by James Gathany

What is Zika virus?

Zika virus (sometimes termed Zika fever) is a Flavivirus that is related to dengue, West Nile, yellow fever, and Japanese encephalitis viruses (Flaviviridae); the viruses are transmitted to humans by mosquito bites and produce a disease that lasts a few days to a week. Common symptoms include fever, rash, joint pain, and conjunctivitis (redness of the eyes). In Brazil, the viral infection has been linked to birth defects (mainly small head and small brain size, termed microcephaly) in babies (newborns) whose mothers became infected with Zika virus during their pregnancy. The CDC reported that researchers now conclude from new data published in the New England Journal of Medicine in April 2016, that Zika virus is responsible for (causes) microcephaly and other serious brain defects. According to CDC Director Dr. Tom Frieden and other experts, these findings should serve as a warning to the U.S. to take Zika virus infections very seriously.

The WHO (World Health Organization) declared Zika virus infections as a public-health emergency in February 2016, after Zika virus had been reported transmitted to humans in 62 countries worldwide.

Medically Reviewed by a Doctor on 8/4/2016


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