Zika ravages mice testes; effect unknown in men

Zika virus ravages the testes of male mice, sharply reducing sperm counts and fertility, says a study that raises a new specter about its threat to people.

Experiments found testes of infected mice shrank about 90 percent by weight, while their output of useful sperm fell by three-quarters on average, and often more. Now it's time to find out if Zika causes similar damage in men, experts said.

"We just don't know that yet," said Michael Diamond of the Washington University School of Medicine in St. Louis, an author of the study. The virus is known to infect a man's reproductive system and persist in sperm and semen.