The Zika Virus Significantly Lowers Fertility in Male Mice

A team of researchers recently made a startling discovery while studying the effects of the Zika virus in laboratory mice. The virus caused damage to the male reproductive system and significantly lowered the fertility of all infected male mice. The findings point to the importance of follow-up studies to determine if the virus affects male humans in a similar way. The details are in a paper that was just published in the journal Nature.

The Zika virus, spread by mosquitoes, is known to cause microcephaly and other birth defects if a pregnant woman becomes infected. This has led doctors to caution pregnant women against traveling to areas with confirmed cases of the virus. Women have also been instructed to wait before trying to get pregnant if there’s any chance they could be exposed to Zika. The virus can also persist in men’s semen for months but the possible consequences have yet to be studied.

Researchers infected male mice with the Zika virus to study possible effects on male reproduction. Within the first week, the virus had entered the testes and began causing inflammation. Over the next few weeks, the testicles shrunk and showed signs of serious damage. The mice produced less motile sperm and testosterone levels dropped. The virus also destroyed Sertoli cells, which normally aid in sperm production. The body stops creating Sertoli cells after development so the loss of these important cells is especially concerning. Infected mice often failed to get healthy females pregnant, even after the virus was out of their system.

The authors point out that a link between the Zika virus and male infertility would be harder to detect than other symptoms. Men are unlikely to discover their infertility until they try to have a baby. While humans may not be affected the same way as mice, the team’s findings emphasize the need for a major study on how the virus affects the male reproductive system.


Govero et al. Zika virus infection damages the testes in mice. Nature (2016).

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