Hantavirus — now at the centre of a growing epidemiological mystery — is raising a troubling possibility: that it can linger in human semen for years and potentially be transmitted through sex.
A peer-reviewed study published in the journal Viruses in 2023 found that the deadly Andes strain of the virus remained in a man’s semen nearly six years after he was first infected.
The study, conducted by researchers at Switzerland’s Spiez Laboratory, a government institute focused on biological and chemical threats, examined a 55-year-old Swiss man who contracted the virus while he was travelling across South America.
Though the virus had disappeared from his blood, urine and respiratory tract, traces remained in his semen 71 months later.
The findings add hantavirus to a small, but unsettling, group of pathogens – including Ebola and Zika – known to persist in what scientists call “immune-privileged” areas of the body, where viruses can evade the body’s usual defences.
The testes, researchers say, can act as a kind of biological safe harbour.
Because sperm cells are protected from attack by the immune system to preserve fertility, certain viruses are able to linger there long after a patient appears fully recovered.
“Taken together, our results show that the Andes virus has the potential for sexual transmission,” the study’s authors wrote, while noting that no confirmed sexual transmission case has ever been documented.
The possibility is drawing renewed scrutiny following the outbreak in April aboard the cruise ship MV Hondius, where health officials have confirmed 10 hantavirus infections and are monitoring dozens of contacts across several countries.
The Andes strain, found primarily in South America, is unusual among hantaviruses because it is believed capable of limited person-to-person transmission.
The outbreak has so far killed three passengers: a Dutch couple and a German woman.
While the World Health Organization (WHO) has said the cluster does not pose a pandemic threat and is “not comparable to Covid”, experts say the new study raises important questions about how recovered patients should be monitored.
Analysts at Airfinity, a health-risk forecasting company, told Britain’s The Telegraph that male patients infected with the Andes strain should receive “extensive safe-sex guidance” even after the standard quarantine period ends.
They recommended protocols similar to those used for Ebola survivors.
Under current WHO guidance for Ebola, male survivors are advised to have their semen tested every three months and are not considered cleared until they receive two consecutive negative test results.
Until then, they are advised either to abstain from sex or use condoms consistently.
The caution stems partly from lessons learned during the 2021 Ebola outbreak in Guinea, which investigators later linked to a survivor of the 2014-2016 West African epidemic who unknowingly transmitted the virus sexually years later.
Whether hantavirus behaves the same way remains uncertain.
Scientists say many factors, including viral load and the virus’ ability to replicate in reproductive tissue, influence how long pathogens can persist in the testes.
