A study has raised fresh concerns about whether hantavirus could potentially spread through sexual contact. Researchers from Switzerland’s Spiez Laboratory found that genetic traces of the Andes strain of hantavirus remained detectable in a man’s semen nearly six years after his initial infection, according to a peer-reviewed study published in 2023. This comes as health officials, including the World Health Organization (WHO), are monitoring an outbreak linked to the MV Hondius cruise ship that has infected at least 11 people and killed three.
What does the study say?
The study followed a 55-year-old Swiss man who contracted the Andes hantavirus during travel in South America in 2016. While the virus disappeared from his blood, respiratory tract and urine during recovery, scientists later identified viral RNA in semen samples taken 71 months after infection.
“Taken together, our results show [the virus] has the potential for sexual transmission,” the research team said.
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Researchers also noted that the male reproductive tract may function as an ‘immune privileged’ site, allowing viral material to persist for extended periods. Similar patterns have previously been observed with viruses such as Ebola and Zika.
The study did not establish that infectious virus remained active for the entire period, nor did it confirm actual sexual transmission years later. However, scientists said the findings demonstrate that such transmission is biologically plausible and deserves further investigation.
WHO investigating how long patients stay infectious
The WHO is, meanwhile, conducting additional studies into the Andes strain after the outbreak aboard the MV Hondius cruise ship. Speaking during a press conference, official Maria Van Kerkhove said researchers are attempting to determine not only whether people are infected, but also whether they remain capable of spreading the virus.
“Essentially what this study will do is to look at regular sampling of individuals who are in quarantine to look at, one, ‘Are they infected?’ but two, ‘Are they infectious?’” she said.
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Health experts say this distinction is important because viral RNA can sometimes remain in bodily fluids long after a patient is no longer contagious.
Scientists urge caution over interpretation
David Safronetz, chief of special pathogens at the Public Health Agency of Canada, warned that detecting RNA alone does not necessarily mean a person can still transmit the virus.
“Just because the RNA is present doesn’t mean that that individual is actively infectious,” he said. “The virus could be inside the immune cells within the body that killed it, but we’re still able to detect the genomic materials.”
Safronetz added that while hantavirus transmission between humans is believed to require prolonged close contact, scientists are still studying whether saliva droplets and other oral fluids may contribute to spread in certain outbreaks.
“There are certain sites in your body, like semen or the eye, called immune privileged sites,” said University of New Mexico immunologist Steven Bradfute.
“Sometimes there’s not as much clearance of pathogens from those areas, but we don’t know if that means it’s infectious or just [represents] the RNA.”
Bradfute also noted that there have been no confirmed cases involving patients transmitting the virus after being discharged from hospital following recovery.
