Hantavirus may still pose a sexual transmission risk even after patients appear to have recovered, with a peer-reviewed study finding that the virus can persist in human semen for years after it is no longer detectable in blood, urine or the respiratory tract.
The finding has raised fresh questions over how long male survivors of infection may remain capable of passing on the virus to sexual partners, including spouses, despite showing no symptoms and having seemingly cleared the infection.
Researchers at Switzerland’s Spiez Laboratory reported that the Andes strain of hantavirus remained detectable in the semen of a 55-year-old Swiss man 71 months after he contracted the virus in South America. Their findings were published in the journal Viruses.
According to the study, the man no longer had detectable traces of the virus in his blood, urine or respiratory tract. However, viral material was still found in semen nearly six years after infection, suggesting the male reproductive tract may serve as a long-term reservoir.
Scientists said this pattern resembles what has already been observed with viruses such as Ebola and Zika, where the testes can provide a form of immune-protected “safe harbor” that allows pathogens to survive long after recovery.
“Taken together, our results show that the Andes virus has the potential for sexual transmission,” the 2023 study said, while noting that such transmission has not yet been documented in humans.
The discovery is likely to strengthen calls for more cautious post-recovery advice for male patients. Health risk analysts have recommended that men infected with hantavirus should receive extensive safe-sex guidance beyond the standard quarantine period, given the possibility that infectious material could remain in semen long after other symptoms disappear.
That advice could mirror protocols already used for Ebola survivors. Under World Health Organization guidance, male Ebola survivors are advised to have semen tested every three months and are not considered clear until they receive two consecutive negative test results.
Until then, they are told either to abstain from sex or use condoms consistently and correctly. They are also advised to wash thoroughly with soap and water after any contact with semen, including after masturbation.
The renewed attention on sexual transmission comes as authorities continue monitoring hantavirus exposures linked to the MV Hondius cruise, where confirmed cases have prompted wider public health concern. In Britain, officials are also monitoring a group of asymptomatic individuals who have been isolating after possible exposure.
It remains unclear what the Swiss study means for those recent cases, particularly because the findings relate specifically to the Andes strain and are based on persistence in one patient rather than confirmed transmission to a partner. Still, public health specialists say the evidence is significant enough to warrant caution.
The testes are already known to act as reservoirs for at least 27 infectious diseases. Because sperm cells are protected from attack by the body’s immune system, viruses can sometimes evade immune clearance in that environment and remain in the body long after apparent recovery.
That phenomenon has had serious consequences in past outbreaks. A 2021 Ebola outbreak in Guinea, which caused 23 cases and 12 deaths, was later linked to a survivor of the 2014-2016 West Africa epidemic who is believed to have transmitted the virus sexually years later.
British health authorities said guidance is being kept under review as more evidence emerges.
The UK Health Security Agency said it continues to monitor international research and that anyone confirmed as a case or identified as a contact in England would be given the necessary public health advice, including steps to reduce the risk of onward transmission.
While there is still no confirmed evidence of human-to-human sexual transmission of hantavirus, the study adds to a growing body of research suggesting recovery may not mark the end of infectious risk for all patients. For spouses and other sexual partners, that could mean the danger persists quietly, long after visible illness has passed.