The World Health Organization greatly broadened its recommendations about sexual transmission of Zika virus Tuesday, advising both men and women who have been in Zika-affected areas to practice safe sex for at least six months.
WHO says more and more studies are showing that sex may pass along Zika more often than anyone thought, and because of the risk to pregnancies it's better to be careful.
And another study showed that Zika virus can be found in tears — at least in mice.
Zika is surprising researchers at every turn and WHO's decision is meant to protect pregnant women as much as possible.
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WHO cited recent studies that show even people who haven't had symptoms of Zika infection might be able to infect other sexually.
"Based on this new evidence, the recommended length of time for safer sex practices for asymptomatic males returning from areas with active Zika virus transmission was extended from eight weeks to six months," WHO said in a statement.
"This is the same length of time as is recommended for symptomatic males. This recommendation now also applies to females, whether or not they have had symptoms. The six-month duration of safer sexual practice upon return has not changed."
WHO also says everyone in Zika-affected areas should have access to counselling and contraception.
Zika's now been shown to cause severe birth defects, especially extensive brain damage, when pregnant women get infected. Most adults who get infected have mild symptoms or no symptoms at all, but the virus can also cause a rare paralyzing condition called Guillain-Barre syndrome.
"The primary transmission route of Zika virus is via the Aedes mosquito. However, mounting evidence has shown that sexual transmission of Zika virus is possible and more common than previously assumed," the WHO said.
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Zika can be found in the blood and it can stay in a man's semen for months. It's also found in urine, but there's no evidence people can pass it to one another that way.
Now, a study published Tuesday showed bits of the virus could be found in the eyes and tears of mice. Mice injected with ground-up eyes from Zika-infected mice also became infected, the researchers report in the journal Cell Reports.
"Even though we didn't find live virus in mouse tears, that doesn't mean that it couldn't be infectious in humans," said Dr. Jonathan Miner of Washington University in St. Louis, who led the study.
"There could be a window of time when tears are highly infectious and people are coming in contact with it and able to spread it," Miner said.
Zika does cause conjunctivitis and eyes are a so-called immune-privileged site, meaning the immune system is not as active there and cannot easily destroy infectious viruses and bacteria.
It's difficult to tell when and how people are infected by a virus when it's spread by mosquitoes, as people living in close quarters not only touch one another but would be vulnerable to bites from the same insects.
Zika has spread across much of Latin America and the Caribbean. It's also spreading in Asia, and it's caused at least two outbreaks in Florida.
Florida officials said Tuesday they have diagnosed seven more home-grown Zika cases in Florida, six of them linked to an outbreak in Miami Beach. Florida now has 56 locally acquired Zika cases.
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Congress returned from a seven-week break Tuesday to a clamor of demands that it approve a budget for the U.S. to fight Zika, but failed almost immediately to move a bill forward.