What is Hantavirus? Symptoms and possible causes behind its spread as cruise ship outbreak raises alarm

A deadly hantavirus outbreak aboard an Antarctic cruise ship went undetected for weeks before health authorities confirmed cases of the rare Andes strain among passengers, sparking concerns over possible human-to-human transmission.

The outbreak has been linked to the MV Hondius, which departed from Argentina for Antarctica on April 1. Three passengers have died, while several confirmed and suspected infections have since been connected to the vessel, according to reports.

Hantavirus is typically transmitted through contact with or inhalation of particles contaminated by rodent droppings. Human-to-human transmission is considered extremely rare, but the Andes strain is among the few known variants capable of spreading between people.

Deaths raise alarm

The first death was reported on April 11, when a 70-year-old Dutch passenger died onboard, according to the World Health Organization.

His 69-year-old wife died on April 26, followed by a German woman on May 2.

Health officials later confirmed that at least two passengers — a British man currently hospitalised in Johannesburg and the Dutch woman — had tested positive for the Andes virus strain, which is largely found in parts of Argentina and Chile.

The UK Health Security Agency said some passengers had already disembarked earlier in the voyage, which travelled from Argentina across the Atlantic toward Cape Verde, though none had shown symptoms at the time.

Symptoms and isolation measures

Experts believe the virus may have spread through close contact aboard the ship, though exposure to infected rodents remains another possible source.

Passengers have since been confined to their cabins while authorities carry out isolation protocols, contact tracing and health monitoring.

The Andes strain can cause Hantavirus Pulmonary Syndrome (HPS), a severe respiratory disease that initially presents with fatigue, fever, muscle pain, headaches and dizziness before rapidly progressing to breathing difficulties requiring urgent medical care.

The mortality rate is estimated to range between 20% and 40%.

Investigators race to trace source

Authorities are still trying to determine where passengers contracted the virus.

Because hantavirus can incubate for up to eight weeks, investigators say exposure could have occurred before departure, during excursions in Argentina or Chile, or onboard the vessel itself.

Argentine officials are tracing the movements of infected passengers through Patagonia and Ushuaia, the southern port city where the ship docked before departure.

Investigators suspect the Dutch couple may have been exposed during a bird-watching excursion near Ushuaia.

Infectious disease specialist Hugo Pizzi said changing environmental conditions may be contributing to the spread.

“Argentina has become more tropical because of climate change, bringing disruptions that allow rodents to proliferate more easily,” he said.

Argentina’s health ministry has reported 101 hantavirus infections since June 2025 — double the number recorded during the previous year.

Once largely confined to Patagonia, officials say 83% of recent cases are now being detected in northern Argentina.

Delayed detection

Health officials in South Africa first began testing for hantavirus after the British passenger in intensive care tested negative for several other infectious diseases.

A positive result was confirmed on Saturday — 21 days after the first death onboard.

The following day, WHO announced it was investigating a suspected hantavirus outbreak linked to the vessel, which had by then reached waters near Cape Verde.

Subsequent testing confirmed the Dutch woman who died after leaving the ship was also infected.

Swiss authorities later said another passenger who had disembarked at Saint Helena had also tested positive.