Zika Virus

Zika virus infection during pregnancy can cause infants to be born with microcephaly and other congenital malformations, known as congenital Zika syndrome. Infection with Zika virus is also associated with other complications of pregnancy including preterm birth and miscarriage. About 2 in 20 (10%) babies of women with confirmed Zika virus infection during pregnancy and about 1 in 20 (5%) had Zika-associated birth defects only in United States.

Among pregnant women in US territories with confirmed Zika virus infection, the proportion babies with Zika-associated birth defects varied by trimester of diagnosis of Zika virus infection:

  • 2 in 25 (8%) in the first trimester
  • Slightly more than 1 in 25 (5%) in the second trimester, and
  • 1 in 25 (4%) in the third trimester.

An increased risk of neurologic complications is associated with Zika virus infection in adults and children, including Guillain-Barré syndrome, a condition in which the immune system attacks the nerves.

No vaccine exists to prevent Zika virus, and there’s no effective antiviral treatment.

Zika virus is transmitted primarily through the bite of an infected Aedes species mosquito, which is found throughout the world. For this reason, it’s likely that outbreaks will continue to spread to new countries. Spread of the virus through sexual contact and blood transfusion have been reported.

Zika outbreaks have been reported in the Pacific Islands, South and Central America, the Caribbean, Africa, and parts of south and southeast Asia.

To date, a total of 86 countries and territories have reported evidence of mosquito-transmitted Zika infection.