Zika Reduces Male Fertility in Mice

Most of the Zika virus impact has focused on women and infants over the past year — and rightly so, given the devastating consequences of microcephaly on a fetus and newborn baby.

But men may not be as immune to devastating effects as previously thought — a new study shows Zika may interfere with men’s long-term ability to have children.

The virus can remain active within the body for months.

Researchers at Washington University School of Medicine in St. Louis, Missouri, found that male mice infected with Zika experienced lasting damage to key cells in their reproductive system — including shrunken testicles, lower levels of sex hormones, and reduced fertility.

Infected mice were four times less likely than healthy males to impregnate a healthy female mouse.

“While our study was [with] mice — and with the caveat that we don’t yet know whether Zika has the same effect in men — it does suggest that men might face low testosterone levels and low sperm counts after Zika infection, affecting their fertility,” said Michael Diamond, M.D., Ph.D., a co-senior author on the study, in a statement.

Health officials have warned men that the virus can remain active within their systems for months — and if there is any chance of exposure to the virus, they should use condoms for six months, regardless of whether they have had symptoms of Zika infection. But until now, men may have believed that was the only consequence.

Related: Zika Health Warning for Men

Further studies are needed, Diamond said, because of the implications. Researchers said this is the only virus to cause such severe symptoms of infertility — and it appears experts are a long way off from a vaccine or treatment for the virus.

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As for fertility, Dr. David Gortler, a pharmacology expert, drug safety expert, and Food and Drug Administration policy expert at FormerFDA.com, agreed more studies need to be done with men specifically. But, he added, “First-world fertility rates have generally been dropping over the past years, prior to the Zika outbreak. It is likely [due to] multiple environmental reasons, but the jury is still out on that one.”

Fortunately, for much of the country, “We’re in the off-season now, so mosquitoes are temporarily on the back burner until next summer,” said Gortler.

But with what is known about the virus — as well as what we still don’t know about Zika — travelers to regions where Zika is still very much active, according to the Centers for Disease Control and Prevention, are warned to continue taking precautions.