A new mouse study published in Nature has found that Zika infection, in addition to harming unborn children, may also interfere with male fertility. Researchers found that just three weeks after contracting the virus, male mice’s testicles had shrunk, levels of their sex hormones had dropped and their fertility was reduced. Researchers found that these mice were less likely to impregnate female mice after being infected with Zika.

"If testosterone levels drop in men like they did in the mice, I think we'll start to see men coming forward saying, 'I don't feel like myself,' and we'll find out about it that way," said co-senior author Kelle Moley, MD, according to a news release.

"You might also ask, 'Wouldn't a man notice if his testicles shrank?' Well, probably. But we don't really know how the severity in men might compare with the severity in mice. I assume that something is happening to the testes of men, but whether it's as dramatic as in the mice is hard to say,” she explained.

No published reports have yet linked infertility in men to Zika infection, but, according to researchers, human studies in areas with high rates of Zika infection are needed to determine the impact of the virus on male reproductive health.

"Now that we know what can happen in a mouse, the question is, what happens in men and at what frequency?" said Michael Diamond, MD, PhD, a co-senior author on the study. "We don't know what proportion of infected men get persistently infected, or whether shorter-term infections also can have consequences for sperm count and fertility. These are things we need to know."

Earlier this year, the World Health Organization declared the Zika Virus — mainly spread by the bite of the Aedes mosquito and sometimes sexual transmission — an international health emergency. Over 65 countries and territories around the world are currently battling transmission of the virus, but researchers are still continuing their search to better understand the disease.

Source: Govero J, Esakky P, Scheaffer SM, Fernandez E, Drury A, Platt DJ, et al. Zika virus infection damages the testes in mice. Nature. 2016.

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