Hantaviruses, which are named after a river in South Korea, describe a family of viruses rather than one single disease.

There are more than 20 different viral species, according to the World Health Organisation (WHO) – almost all of them linked to infection by rodents, typically rats and mice, through dried urine and droppings.

But one strain, known as Andes virus, is thought to spread by human-to-human transmission, although very rarely. It has now been identifed in passengers on the cruise ship.

The Andes virus is mostly found in Argentina and Chile.

In late 2018, there was an Argentinian outbreak that was traced back to people who had attended a party – a single person with the virus is thought to have unwittingly spread the virus to 34 confirmed cases, with 11 deaths.