Preventing Sexual Transmission of Zika Virus

Zika virus infection is widespread in Latin America, with some cases also reported in the U.S. and elsewhere. Most cases of Zika are transmitted through the bite of an infected mosquito (Aedes aegypti, the same species that can transmit dengue). However, Zika can be transmitted by two other modes: Fetal infection via the placenta of infected pregnant women; and sexual transmission from men to women.

Although Zika infection is often asymptomatic, it can cause mild fever, joint pain, and rash. Maternal infection during pregnancy has been associated with microcephaly and other congenital defects in offspring. In addition, incidence of Guillain-Barré syndrome is increased following Zika virus infection.

Data about the specific timing of Zika virus infection and risk for fetal damage continue to accrue. Among characterized cases of fetal microcephaly, symptomatic maternal infection during the first trimester of pregnancy is of greatest concern. However, lack of understanding about the duration of viremia, persistence of Zika virus in immunoprivileged sites (such as semen or placenta), and other relevant risk factors limit the ability to make definitive recommendations. The CDC's interim recommendations are as follows:

For pregnant women:

• Healthcare providers should query pregnant women about recent travel.

• Pregnant women who have traveled in regions where Zika virus is circulating should be tested for Zika virus infection.

• In pregnant women with symptoms consistent with Zika virus, blood can be tested by RT-PCR. In women with histories consistent with Zika virus infection, IgM and neutralizing antibody tests are recommended. Notably, cross-reactivity with other flavivirus infections may occur.

• Women with confirmed infection should be managed by a maternal-fetal medicine provider or an infectious disease specialist with expertise in pregnancy.

• Women who are pregnant or considering pregnancy should consider postponing travel to areas with Zika virus transmission.

For women and men considering travel to areas with known Zika virus transmission:

• Mosquitoes that transmit Zika virus are daytime biters; thus, bed nets alone are insufficient.

• Long pants and long sleeves are recommended to reduce risk for mosquito bites.

• Permethrin-treated clothes and air conditioning are beneficial.

• Insect repellent containing DEET, picaridin, and IR3535 should be applied per label.

Whereas half of pregnancies in the U.S. are unintended, many countries in Central and South America lack readily accessible birth control (especially highly effective methods), further hampering contraception. Men returning from areas with Zika virus transmission — and whose partners are pregnant — should abstain from sexual intercourse or use condoms consistently throughout the pregnancy.