Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito (found in Africa, Southeast Asia, and the Pacific Islands, Centreal and South American, including Brazil, Commonwealth of Puerto Rico, the U.S. Virgin Islands, and America Samoa).
The mosquitoes become infected when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites. There have been documented cases of Zika virus being passed from blood transfusion or sexual contact. The documented cases that have occurred in the United States from sexual contact have arisen from contact with a person returning from areas of the world that Zika Virus is known.
The CDC feels that these local outbreaks have and will continue to occur as a result of virus importation by infected, viremic travelers but since the native mosquito is the primary cause of transmission, there is not likely to become widespread transmission through this sexually transmitted route.
An estimated 80% of people infected with Zika virus do not have symptoms. For people that are infected that have symptoms, they generally are mild and characterized by acute onset of fever, rash, joint pain, conjunctivitis (red/pinkness to whites of the eyes without drainage), headache and body aches. The incubation period (the time from exposure to symptoms) is not known, but is likely to be a few days to a week. Symptoms usually last from several days to 1 week. Severe disease requiring hospitalization is uncommon, and fatalities are rare. Guillain-Barré syndrome, a rare disorder in which your body’s immune system attacks your nerves, has been reported in patients following suspected Zika virus infection.
Pregnant women can be infected with Zika virus in any trimester. No evidence exists to suggest that pregnant women are more susceptible to Zika virus infection or experience more severe disease during pregnancy versus non-pregnant women.
Transmission of Zika virus from the pregnant mother to her fetus has been documented. Zika virus genetic material has been detected in breast milk, but Zika virus transmission through breastfeeding has not been documented.
Zika virus infections have been confirmed in infants with microcephaly, which is a rare neurological condition in which an infant’s head is significantly smaller than the heads of other children of the same age and sex. Microcephaly usually is the result of the brain developing abnormally in the womb or not growing as it should after birth. It can be caused by a variety of genetic and environmental factors. Children with microcephaly often have developmental issues.
In the current outbreak in Brazil, a marked increase in the number of infants born with microcephaly has been reported, but it is NOT KNOWN how many of the microcephaly cases are associated with Zika virus infection. Studies are under way to investigate if there is an association with the Zika virus infection and microcephaly.
Because there is neither a vaccine nor prophylactic medications available to prevent Zika virus infection, CDC recommends that all pregnant women consider postponing travel to areas where Zika virus transmission is ongoing. There is no specific antiviral treatment available for Zika virus disease. Treatment is generally supportive and can include rest, fluids, and use of pain relievers and fever-reducers. Fever should be treated with acetaminophen (Tylenol). NSAIDs like ibuprofen (Advil and Motrin) should be avoided.
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