News that British long jumper Greg Rutherford is freezing his sperm ahead of the Rio Olympics raises an important and overlooked question. How important is the Zika outbreak to men? The answer, based on current evidence that it can be spread sexually, is very.

With close to a dozen countries reporting birth defects among the infants of mothers infected with Zika, women have been the focus. To be sure, mothers are paying an incredible price in this epidemic, and face a more uncertain future if infected during pregnancy. But placing the onus of safety entirely on them misses the point and threatens to extend the life of the outbreak.

Unlike its sister viruses, like dengue fever, Zika can be spread sexually. So although the mother may be the one passing Zika on in the womb, it’s an infection that may have originated with the father. Considering men’s role in this outbreak is critical.

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Since the Zika outbreak began in May of last year, 60 countries and territories have reported spread of the virus. The infection itself is relatively mild and remains undetected in the majority of cases. But it has been linked to a smattering of serious long term side effects, not all of them congenital.

In April, scientists at the Centers for Disease Control and Prevention (CDC) concluded the virus is indeed the cause of a spike in fetal brain defects worldwide, specifically microcephaly. Characterized by an underdeveloped brain and skull, it’s a condition that has been reported in 11 countries with Zika—nearly 5,000 (suspected and confirmed) cases in Brazil alone.

While scientists initially believed that the infection left the body in under a week, new evidence suggests that it remains in sperm. This week the World Health Organization (WHO) reported that 13 countries have now seen human-to-human transmission of the disease, noting that it is “probably via a sexual route.”

Non-pregnant women usually rid their bodies of the disease within seven days, according to the CDC. “Based on the available evidence, we think that Zika virus infection in a woman who is not pregnant would not pose a risk for birth defects in future pregnancies after the virus has cleared from her blood,” the organization states.

For men it’s a different story. The CDC reports that males can pass on Zika before their symptoms start, while they are present, or even after they end. “Zika virus can stay in semen longer than in blood, but we don’t know exactly how long Zika stays in semen,” the information page reads. Men who have never shown symptoms may even be able to pass on the virus.

There is no evidence that women, at any stage, can do the same.

“The Zika news has caused no end of concern if we’re totally honest,” Rutherford’s partner Susie Verrill wrote in Standard Issue Magazine on their decision to freeze his sperm. “We’re not ones to worry unnecessarily, but after more than 100 medical experts stressed the Games should be moved to prevent the disease from spreading, this was a huge factor in us choosing to stay put.”

The couple, who already has one child, said they didn’t want to face an uncertain future.

“We’d love to have more children and with research in its infancy, I wouldn’t want to put myself in a situation which could have been prevented,” Verrill wrote. “Specialists still also don’t know the ins and outs of Zika, so even though it looks as though there’s no real issues should Milo get bitten, it’s just another thing we don’t want to chance.”

Beyond birth defects, the virus has been linked to a serious nerve disorder called Guillain Barre Syndrome (GBS), a condition in which the immune system attacks the nerves. Thirteen countries have reported a rise in GBS cases since the outbreak began. GBS, which can cause temporary paralysis, is more common in older people, specifically men.

The question of how long the virus remains in sperm is a difficult one. Thus far, researchers have found it in the sperm of men who were infected up to 62 days after the initial symptoms. One of the first instances of sexual transmission of the virus was reported in the U.S. in 2011, when a man infected his wife with it after returning from a trip to Senegal.

During this current outbreak, there have been six reported cases of sexual transmission in the U.S., one of which was male to male. The WHO and CDC recommend that men who have traveled to Zika-affected areas wait at least eight weeks before having sex, if it’s intended end in pregnancy. Men who have been infected with the virus should wait six months.

For Rutherford’s partner, missing the games in order to avoid putting herself at risk is worth it. For him, freezing his sperm is too. The decision will likely help to spark vital conversation around men’s role in the Zika epidemic. And no matter his fate at the games, Verrill will be patiently awaiting his return at home.

“Good luck to my favorite,” she ended the piece. “Win or lose, I still won’t change the locks.”