While one study showed hantavirus may be found in semen for years, no research yet confirms this indicates long-term contagiousness

Researchers say the hantavirus may have greater staying power than expected in some human hosts.  

The recent outbreak aboard the MV Hondius cruise ship has heightened the urgency of questions that remain about the potentially fatal disease. 

Thought generally to spread through inhalation or ingestion of urine, feces, and saliva from infected rodents, climate shifts and habitat changes affecting the animals may impact transmission rates. Meanwhile, the Andes strain — confirmed to have affected the ship's passengers — appears capable of human-to-human transmission, raising more concerns about contagion timelines.

To address such questions and concerns, Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization, announced in a May 15 briefing that the agency is "working with more than 20 countries to coordinate studies to better understand the natural history of the disease," which can cause severe respiratory problems and flu-like symptoms. 

Some previous research has found that the Andes strain may remain detectable in bodily fluids for years after exposure. Scientific American reported on a single study published in Viruses in 2023 that found the virus's RNA present in the semen of a Swiss man in 2022 after he tested positive in 2016 following travels in South America. 

But researchers stress this doesn't necessarily mean an infected person will remain contagious for extended periods.

"Just because the RNA is present doesn't mean that that individual is actively infectious," David Safronetz, Chief of Special Pathogens at the Public Health Agency of Canada, told Scientific American. "The virus could be inside the immune cells within the body that killed it, but we're still able to detect the genomic materials."

Various viruses have been found to linger in semen and other bodily fluids, such as ocular fluid and breast milk. While the presence of hantavirus RNA might suggest the possibility of sexual transmission, Safronetz told the outlet that has not been established.

Still, the Centers for Disease Control and Prevention has encouraged people to "[avoid] kissing and sexual contact with someone who may have Andes virus" to reduce the risks of transmission. This is likely intended to reduce the risk of inhaling or otherwise ingesting saliva droplets while in close personal contact with an infected person.

While questions about the Andes strain persist, experts generally agree that climate shifts and habitat changes are affecting the spread of diseases such as hantavirus. 

Isabel Gómez Villafañe, a researcher at the Institute of Ecology, Genetics, and Evolution at the University of Buenos Aires, told WIRED that rising humidity, milder winters, and more expansive summers can lead to increases in rodent populations, spurring transmission spikes. Higher numbers of potential vectors — as well as higher chances of humans coming into contact with them through urbanization and land-use changes — could prompt the spread to humans.

"We are constantly invading natural environments," hantavirus researcher Karina Hodara told WIRED. "[...] And that increases the chances of contact for us."

In a short video shared on social media, Scientific American reporter Adam Kovac indicated that coverage of the 2023 study published in Viruses may have stirred some panic and even misinformation online. 

"[It] doesn't necessarily mean you can catch hantavirus through sex with someone years after they had it," Kovac said in the video. "Some pathogens can remain in the body for years, and whether infection can ensue can vary virus by virus, and we just don't know enough about hantavirus yet."

Kovac also noted that there is currently no specific treatment for hantavirus but that researchers hope new attention to the disease may prompt increased funding for treatment development.

At a May 12 press conference, Ghebreyesus stated that the global health risks posed by the recent hantavirus outbreak were low, given the nature and circumstances of the infections. But he noted that the WHO would be monitoring the situation.

"Given the long incubation period of the virus, it's possible we might see more cases in the coming weeks," he said. 

Eleven cases of hantavirus have been documented in connection with the cruise ship, two of them presumptive. Three people have died as a result of the outbreak as of May 22.

Kirsten Krueger contributed to the editing of this article.