Sexual Transmission of Zika Virus and Pregnancy Outcomes in the U.S.

Infection with Zika virus has attained epidemic proportions in parts of the Americas. Cases have now been reported in U.S. women who did not travel to endemic areas or were not in locales in which the mosquito existed during the season of acquisition, but who had sexual exposure to males who had recently traveled to such areas.

During February 6 to 22, 2016, 14 cases involving suspected sexual transmission, based on the above criteria, were reported to the CDC from multiple states. Two laboratory-confirmed cases and four probable cases of sexual transmission were culled from these reports. Several women involved were pregnant. Contact included vaginal sex without condom use that occurred while, or shortly after, the male partner experienced symptoms consistent with Zika virus infection. No cases have been reported of sexual transmission from asymptomatic males to females or from infected females to males.

Another report from the CDC presents data as of February 17, 2016, on pregnancy outcomes in nine U.S. women with Zika virus infection who had traveled to affected areas. Outcomes included two early pregnancy losses; two elective terminations; three term births, one of which involved an infant with severe microcephaly; and two in-progress pregnancies. An additional 10 cases are under investigation. Screening for Zika infection is available from the CDC for pregnant women traveling from endemic areas. Of 257 pregnant women who were tested from August 1, 2015, through February 10, 2016, 97% were Zika-negative, and 3% were Zika-positive. Among the Zika-positive group, no hospitalizations or deaths have been reported.