Hantavirus can persist in semen for years, but that doesn’t mean it remains contagious

Hantavirus can persist in semen for years, but that doesn’t mean it remains contagious

By Adam Kovac edited by Claire Cameron

The deadly hantavirus that caused a cruise ship outbreak that is believed to have sickened at least 10 people and killed three of them may be transmissible through many bodily fluids ranging from saliva to breast milk to semen, but how long it remains transmissible after a person becomes infected is a mystery.

At a news conference Friday, World Health Organization (WHO) officials said numerous studies were underway on the Andean type of hantavirus, which began spreading among passengers and crew aboard the MV. Hondius in April. Among those investigations is an attempt to clarify how long people carrying the virus remain contagious, said Maria Van Kerkhove, who heads the WHO’s emerging diseases and zoonoses unit. WHO is currently setting up a natural history study that will examine the life cycle of the virus in human hosts, she said. This knowledge is particularly important, given that there is no specific treatment for hantavirus yet.

“Essentially, this study will look at a regular sampling of quarantined individuals to determine, first, ‘Are they infected?’ but secondly: “Are they contagious?” “, she said.

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Establishing the latter can be tricky. The virus’s RNA may remain detectable in human bodily fluids long after the risk of infecting another person has passed. At least one case study indicates that viral RNA can persist in human bodily fluids for years after infection. In this case, a then 55-year-old Swiss man who had traveled from Ecuador to Chile in 2016 began showing symptoms of hantavirus after returning home; he tested positive for the Andes type. In a follow-up examination six years after infection, remnants of the virus’s RNA were found in the man’s semen.

However, the presence of viral RNA in body fluids after an infection is not necessarily a sign of danger, says David Safronetz, head of special pathogens at the Public Health Agency of Canada. “Just because RNA is present doesn’t mean that individual is actively infectious,” he says. “The virus could be inside the body’s immune cells that killed it, but we are still able to detect the genomic material.”

The presence of the virus in semen hints at the possibility of sexual transmission, but Safronetz says it’s hard to say conclusively. Based on previous Andean-style outbreaks, hantavirus would require close, prolonged contact to spread from one person to another — the kind of proximity that might result from living in close proximity or having sex. But some outbreaks, like the current cruise ship fire, suggest the virus may not need such close, prolonged contact to spread in some cases. The prevailing scientific theory, which has not been definitively proven, is that Andean hantavirus likely spreads from person to person through aerosolized saliva droplets and other oral fluids that carry a high viral load.

Many viruses can persist in semen for years, says Steven Bradfute, an immunologist at the University of New Mexico, and whether the pathogen remains infectious can vary from virus to virus.

“There are certain sites in your body, like the sperm or the eyes, called privileged immune sites,” he says. “Sometimes pathogens aren’t cleared from these areas as much, but we don’t know if that means they’re infectious or just infectious. [represents] RNA.

For people who test positive for hantavirus RNA, additional blood tests can determine whether they are still contagious, he adds. Bradfute says there have been no documented cases of infection by someone discharged from a health care facility after recovering from a case of Andes-type hantavirus.

The WHO insists that the hantavirus outbreak poses no danger to the public, and Safronetz notes that anyone who has exhibited symptoms or is on the cruise ship or in contact with any of the ship’s passengers is subject to some form of close monitoring and regular testing. In the case of cruise ship passengers, many will not leave quarantine until at least 42 days after their last exposure to the virus. The chances of any of them being contagious after that point are virtually zero, Safronetz says.

“If you take a sample at day 45 and these individuals are still negative for Andes virus, then the likelihood that they were exposed in the first place is very low,” he says. “Actually, it’s probably negligible, because the virus would have done something at that time. That’s just based on 30 years of epidemiological experience.”

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