At least 27 viruses are found in human semen. While some of them, such as HIV, hepatitis C, and herpes, are well known and can be sexually transmitted, others may surprise you.
That’s the finding published by the Centers for Disease Control and Prevention in a November 2017 research letter. Although public health experts have known for decades that certain infectious agents can be found in human semen, scientists have made some recent discoveries that have expanded that list.
Researchers have learned, for example, that the Ebola virus can persist in human semen for more than a year after infection. And Zika, a virus transmitted by a mosquito that can cause severe birth defects, can be found in semen. Most worrisome, it is possible for a man to transit the virus sexually to his partner.
It was the discovery that Zika virus can persist in human semen that prompted researchers to wonder what other bugs might be lurking within seminal fluid and testicular tissue. They scoured the literature to see what research had been done and came up with evidence for 27 different types of viruses that could be found in semen, including chikungunya, Ebola, Epstein-Barr, Lassa fever, Marburg, and Zika.
What you should know
Although it’s possible that semen can contain many types of viruses, that doesn’t mean that they all can be sexually transmitted, cautions John Swartzberg, M.D., professor emeritus at the University of California, Berkeley, School of Public Health.
“In heterosexual sex, the virus may not be able to survive in the vagina, or it may not be able to infect vaginal or cervical cells,” Swartzberg told HealthCentral in an email interview. “Epidemiologic and laboratory studies have proved that viruses such as cytomegalovirus and HIV can be transmitted by semen. But we do not have this kind of data for most of the other agents.”
He also cautions that some of the viruses reported in the research letter were found in tissue from the testicles, not in semen itself. The authors of the report speculate that if a virus is present in the testes, it could also be present in human semen.
The bottom line
While it’s unclear how many of these viruses can actually infect someone who comes into contact with semen, the best precaution is to use condoms for protection, Swartzberg says. “The role of semen in transmitting these viruses to others is unclear at this point,” he says. “But we have to assume it can occur and take every appropriate precaution.”