infections
Zika Virus Infection
Transmission of Zika Virus
During the first week of infection, Zika virus is present in blood. When mosquitoes bite an infected person, they ingest blood containing the virus. The virus replicates in the mosquitoes and, after a few days, when the mosquitoes bite another person, they can transmit the virus to that person. People who have traveled to areas where Zika virus infection is common may have Zika virus in their blood when they return home. If they live in an area withAedesmosquitoes, the mosquitoes may bite them, then spread the virus to other people living in the area, resulting in local transmission of the Zika virus. Although the Zika virus is usually spread by mosquitoes, it may be spread in other ways: Sexual intercourse (vaginal, anal, or oral sex) and the sharing of sexual devices An infected pregnant woman to her baby before or during birth Blood transfusion or organ transplantation People with Zika virus infection can transmit the virus through sexual intercourse in many circumstances: If the infection never causes any symptoms Before their symptoms start While they have symptoms After their symptoms end Zika virus remains in semen much longer than it remains in blood and other body fluids. It can be spread by infected men to their sex partners (male or female) through unprotected (no condom) sexual intercourse, including vaginal, anal, and oral sex (see alsoZika: Sexual Transmission and Prevention). The Zika virus also remains in vaginal fluids after it disappears from blood and urine. Infected women can spread the virus to their male partner during sexual intercourse. Transmission by blood transfusion has been reported in Brazil. However, no cases of transmission by blood transfusion have been confirmed in the United States. The Zika virus can be spread from mother to child during pregnancy or around the time of birth. At present, there have been no reports of infants becoming infected with Zika virus through breastfeeding. Even though the genetic material of Zika virus has been found in breast milk, risk of transmission from breast milk is outweighed by the nutritional benefits of breast milk for the infant. (SeeCenters for Disease Control and Prevention [CDC]: Zika TransmissionandWorld Health Organization [WHO]: Guideline: infant feeding in areas of Zika virus transmission, 2nd edition.) 