Liz Szabo

USA TODAY

Some sperm banks and fertility societies are taking steps to keep the Zika virus out of their supplies of donor sperm to avoid infecting women trying to get pregnant.

Zika virus, which has spread quickly throughout Latin America and the Caribbean, is primarily spread through mosquito bites. But because the virus also can be transmitted sexually and through blood transfusions, some are concerned that sperm donated by men who have traveled to countries with outbreaks could pass the infection to women trying to become pregnant.

Although the Zika virus doesn't tend to make people very sick, it has worried health authorities around the globe because of its link to an increase in serious birth defects in Brazilian babies.

U.S. fertility associations have not issued guidelines yet on Zika virus.

There are no commercial tests for Zika, so clinics can't screen blood or semen for Zika, the way they already do for diseases such as HIV and hepatitis. Only labs at the Centers for Disease Control and Prevention and a handful of states today are capable of diagnosing Zika.

But the British Fertility Society released recommendations Monday, stating that people who have traveled to areas with Zika outbreak should not try to conceive naturally, donate sperm or eggs or undergo fertility treatments for 28 days. The Zika virus is believed to stay in the blood for less than 28 days after a person is bitten.

Scientists don't know how long the Zika virus can survive in semen, or whether the virus is present in the semen of men without symptoms, said Harvey Stern, medical director at Fairfax Cryobank, located in Northern Virginia.

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The CDC has recommended that pregnant women postpone travel to places affected by Zika and to abstain from sex or use condoms if their "male sexual partner has traveled to or lives in an area with active Zika virus transmission."

AABB, formerly known as the American Association of Blood Banks, recommended Monday that blood suppliers ask people to postpone donating blood for 28 days if they have traveled to a country with a Zika outbreak. The American Red Cross has adopted that recommendation.

California Cryobank, a sperm bank with clinics across the country, is adopting an even more stringent policy. Its clinics won't accept sperm donations from men who have traveled to countries with Zika outbreaks in the past month or who have had sex with someone who has traveled there within the past month, said Charles Sims, California Cryobank's medical director.

California Cryobank already asks regular donors to report any travels outside the USA or Canada, Sims said. The company plans to check its records on where sperm donors have traveled over the past year to see if any have visited the nearly 30 countries and territories where the virus has caused outbreaks.

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Sperm banks are already required to keep donations in "frozen quarantine" for six months to make sure specimens are disease-free, said Owen Davis, president of the American Society for Reproductive Medicine. It can take six months for tests to detect HIV in a person's blood, for example.

Clinics may need to revise their policies as scientists learn more about Zika virus, Stern said.

About four of five people infected with Zika have no symptoms, according to the World Health Organization. Those who do develop symptoms tend to have mild illness, including a low fever, rash, headache, joint pain and pink eye.

Scientists first detected the Zika virus in Uganda in 1947. But the disease didn't appear in the Western Hemisphere until May, when Brazil reported its first cases. Until last fall, Zika had never before been associated with birth defects.

Doctors were surprised last year by the first documented cases of sexual transmission of Ebola, which occurred in Liberia. Although researchers knew that Ebola could survive in semen for several weeks, they were surprised when studies showed that Ebola can survive in semen for at least nine months.

Scientists don't know whether Zika can be transmitted through solid organ transplants, according to a statement issued Thursday from several leading transplant groups. Transplant centers should balance the risk of Zika infection with the potential benefits in someone who needs an organ transplant, according to the statement, from the Organ Procurement and Transplantation Network, United Network for Organ Sharing, the American Society of Transplantation and the American Society of Transplant Surgeons.