Viral load.

As health officials continue to monitor the rare and deadly Andes strain of hantavirus that spread across the MV Hondius cruise ship, a disturbing truth about the disease’s long-term transmissibility has emerged.

A peer-reviewed study found that hantavirus can survive in human semen for up to six years and can be sexually transmitted even after a patient has fully recovered.

Publishing in the journal Viruses, researchers from the Spiez Laboratory in Switzerland looked at a 55-year-old man who had been infected with the Andes strain six years prior to the study.

The virus was completely gone from the man’s blood, urine and or respiratory tract. But it was still lurking in his semen.

They concluded that it might still be transmittable to others for up to 71 months after infection.

The team found that while there were no traces of the virus in the man’s blood, urine, or respiratory tract, hantavirus was detectable in his semen and potentially transmittable to others for up to 71 months — or five years and 11 months — after infection.

Because sperm is required to prorate, the body’s immune system won’t attack them. That means that some viruses — including hantavirus, Ebola and Zika can stealthily remain in the male testes, even as the body fights them off elsewhere.

Researchers call the testes a “safe harbor” for at least 27 infectious diseases, allowing pathogens to persist in the body and infect others years after an infected patient has recovered.

Whether a virus stays in the testes comes down to a few factors, including viral load (how much of the virus was in the bloodstream to start with) and the virus’s ability to replicate within the male reproductive tract. 

And it means that a man could possibly pass the virus on to a sexual partner.

“Taken together, our results show that the Andes virus has the potential for sexual transmission,” study authors said, although they maintain that a case of sexually transmitted Andes virus has never been documented. 

Indeed, a 2021 Ebola outbreak in Guinea, which resulted in 12 deaths, was later found to have originated with a man who survived the epidemic of 2014-2016 and then unknowingly spread the virus through unprotected sex.

As with viruses like Ebola, male hantavirus patients are advised to change their sexual practices.

The World Health Organization recommends that Ebola survivors have their semen tested every three months and are not “cleared” for unprotected sex until they record two consecutive negative test results.

Until cleared, they should “abstain from all types of sex” or “use condoms consistently and correctly.” 

They should also wash themselves “thoroughly” with soap and water after any contact with semen — including after masturbation, according to the guidance.

Experts, including those at the disease forecasting company Airfinity, a disease recommend that survivors of the Andes strain follow suit.

Affinity stressed to The Telegraph that male hantavirus patient guidance should be “analogous to the World Health Organization’s Ebola survivor semen-monitoring protocols,” and that hantavirus survivors should receive “extensive safe-sex guidance beyond the [42-day] quarantine.” 

The outbreak of the Andes hantavirus, which is primarily spread by rodents but can be transmitted between people in rare cases, was reported in early May aboard the MV Hondius, a luxury expedition cruise ship.

It has since killed three people: a Dutch couple and a German national.

The WHO said on Tuesday that more cases were expected from the cluster linked to the ship, but stressed ⁠that it was not comparable to COVID and did not pose a pandemic threat.