Why rat virus patients could become super-spreaders

The Andes strain of hantavirus behind the outbreak on a cruise ship is susceptible to “super-spreader” events, according to research backed by the US military.

Three people have died on the Dutch vessel MV Hondius and three others are sick with suspected hantavirus infection.

More than 140 people are stuck in quarantine and cannot disembark the ship because the rodent-borne virus is thought to be caused by a strain which can spread between humans.

The US Army Medical Research Institute of Infectious Diseases – historically known as the centre of the US biological weapons programme – now focuses on biosecurity and, in 2020, backed groundbreaking research that showed the Andes strain of hantavirus can spread rapidly between people.

The researchers, based at Fort Detrick, Maryland, also found that symptomatic individuals were capable of causing “super-spreader” events given the right social circumstances, such as those found on cruise ships.

“After a single introduction [of Andes hantavirus] from a rodent reservoir into the human population, transmission was driven by three symptomatic persons who attended crowded social events,” the researchers found in a 2018-2019 outbreak in Chubut Province, Argentina, which resulted in 34 confirmed infections and 11 deaths.

“Our findings traced the first person-to-person transmission event to a birthday party with approximately 100 guests,” said the researchers, whose work was published in the New England Journal of Medicine.

The “index patient” was found to have infected five others during “90 minutes” at the party. The second person infected was found to be the “likely source” for six further cases and, after his death, his wife infected an additional 10 people at his wake.

“It appears that inhalation of droplets or aerosolised virions may have been the routes of infection,” added the researchers.

Despite medical experts acknowledging that human-to-human spread of hantavirus is rare, these findings do not bode well for those on the cruise ship as it makes its way from Cape Verde to the Canary Islands, where it is to be evacuated.

Human-to-human transmission could explain why a British doctor fell ill after treating patients on the ship, and may account for the images of medical workers in full bio-protection gear on board the stricken vessel.