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    Zika Virus: What You Should Know

    Zika virus is “spreading explosively” in the Americas, the WHO says. It causes birth defects in babies born to pregnant women, says the CDC. That agency has issued travel warnings for pregnant women in countries where the disease is spreading. The virus is mainly spread by mosquitoes, although cases of sexual transmission have been reported.

    What is Zika? How can you avoid it? WebMD answers your questions.

    What is the Zika virus? How do you catch it?

    aedes albopictus mosquito

    Zika virus, first identified in Uganda in 1947, is transmitted by the same type of mosquito that carries dengue fever, yellow fever, and chikungunya virus. A mosquito bites an infected person and then passes those viruses to other people it bites. Outbreaks did not occur outside of Africa until 2007, when it spread to the South Pacific.

    CDC Director Tom Frieden, MD, told reporters that “on occasion,” Zika may be spread through sexual contact or blood transfusions. The CDC has confirmed reports of Zika being spread through sex in some cases, meaning a person traveled to an area where Zika has broken out, got the virus, and gave the virus to a sexual partner who did not travel.

    The CDC is aware of a report that Brazilian scientists have found the virus in the saliva and urine of infected people, Frieden said, but more information is needed.

    What are the symptoms of Zika virus?

    The disease can cause fever, rash, joint pain, and redness in the whites of the eye. But most people won’t know they have it.

    “Only about 1 in 5 people with the virus will exhibit symptoms,” says Amesh Adalja, MD, a spokesman for the Infectious Diseases Society of America. “The vast majority have no symptoms at all.”

    Zika has "never been thought of as a severe infectious disease until now," Adalja says.

    But in rare cases, Zika has been associated with Guillain-Barre syndrome, a disorder that can cause partial or complete paralysis, usually starting in the legs, most often temporary. An increase in that illness has been seen in areas such as French Polynesia and Brazil, where a Zika epidemic has taken place. A study released Feb. 29 suggested Zika may cause the syndrome but could not prove it.

    One U.S. case of Guillain-Barre that may be tied to Zika has been reported to the CDC, Frieden said. But “it’s very challenging to make the link in an individual case,” he said, as Guillain-Barre can also follow the flu or other infections.

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