Zika may persist in vagina for days: study

WASHINGTON, Aug. 25 (Xinhua) -- The Zika virus may reproduce in the vagina of pregnant women several days after infection, from where it spreads and infects the fetal brain, impairing fetal development, a mouse study suggested Thursday.

Zika is commonly transmitted through a bite from an infected mosquito, and recent reports have confirmed it's also capable of leaping from person to person through sexual transmission. However, researchers have not determined whether the Zika virus replicated in the vagina after women were exposed through sexual intercourse.

In the new study published in the U.S. journal Cell, researchers from the Yale University observed replication of the Zika virus in the vaginal tissue of wild-type mice and mice genetically modified to be susceptible to Zika. Normally, mice cannot be infected by the virus.

The researchers found that the Zika virus replicated in the vagina and persisted post-infection, even in normal mice.

"We saw significant virus replication in the genital tissue, up to four to five days," said senior author Akiko Iwasaki, an immunobiologist at Yale University.

"What surprised us most was that the virus replicated in the vagina of wild-type mice," said Iwasaki.

This prolonged presence of the virus has not been observed in other sites of infection in wild-type mice, she said.

The team also detected Zika virus in the fetal brains of mice, and that infection was associated with fetal weight loss.

"Early during pregnancy, if the mother is infected, there is significant impact on the fetus, even in wild type mice," she noted.

While the immune response to Zika virus is different in people, the study results raised critical questions about the impact of sexual transmission.

"The finding may be important for women, not only pregnant women," said Iwasaki. "The vagina is a site where the virus can replicate and possibly transmit to partners. In pregnant women, vaginal transmission of Zika virus may have a significant impact on the developing fetus."