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Zika Virus and Sexual Transmission: The Facts


More and more is coming to light about the Zika virus. The Centers for Disease Control and Prevention have now confirmed that a case of Zika was sexually transmitted to a person in Texas. However, while this enhances what we know about transmission of the illness, it doesn't change what we know about its severity. "Although this may cause a lot of excitement in the press, there is no reason to panic," says Andrew Pavia, MD, the chief of Pediatric Infectious Diseases for University of Utah Heath. "We still think Zika virus is only likely to be a significant problem for pregnant women."

Pavia also points out this isn't the first time Zika has been sexually transmitted. The question is how often Zika is transmitted in the semen of an infected male. "The first reported case of possible sexual transmission in 2008 was in a man who saw blood in his semen," he says. "He also had symptoms of prostate infection at the time he might have transmitted. The virus was also detected in the bloody semen of a man in Polynesia with Zika. What we don't know is how rare this complication is in men with Zika virus infection or how often the virus can be transmitted by sex with an infected man."

While transmission through sexual contact may be very rare, that doesn't mean precautions shouldn't be taken. "If a pregnant woman is infected through sex, this would likely have the same risk as mosquito-acquired disease," says Sankar Swaminathan, MD, chief of the Division of Infection Diseases for University of Utah Health. "Also, it is possible that pregnancies that result from sex with an infected partner could be at risk for birth defects."

Pavia says another possibility is miscarriages in pregnancies that occur involving Zika infected sperm. However, any hypotheses have no backing at this point. "So far there are no reports of pregnant women infected through sex so we just don't know," Pavia says.

Both Pavia and Swaminathan say that until we know more about this method transmission, condoms should be worn by men who may be infected with the Zika virus with pregnant partners. "This would include men who have travelled to a Zika endemic area and have symptoms, or those who may have had mosquito bites in an area where Zika is being transmitted," says Pavia. "We expect to see guidance from CDC with more details in the near future."

Swaminathan adds this is especially important with men who may not be symptomatic. "If one takes the one previously documented case at face value, the male may transmit the virus prior to symptoms," he says. "Some countries are advising that men who have traveled to a country where a Zika outbreak is present should wear condoms during sex for 28 days. They are also being advised to take these precautions for 6 months if they had an illness compatible with Zika virus infection. Travelers to these areas should also defer blood donation," he adds, "as Zika virus has been found in donated blood products."