Fears Grow Over Hantavirus 'Generation 3' Transmission, but the WHO Says the Threat to the Public is Low

By early May 2026, a deadly hantavirus outbreak aboard the expedition cruise ship MV Hondius had claimed the lives of three passengers, including a Dutch husband and wife and a German woman.

Health authorities identified the infections as the Andes strain of hantavirus, prompting officials to classify the situation as a level 3 emergency due to concerns over possible human-to-human transmission.

Wider Hantavirus Spread Unlikely

The World Health Organisation (WHO) reported that as of 11 May, there were nine confirmed infections and two additional suspected cases connected to the infection from the MV Hondius. The ship, carrying 149 passengers and crew members, became the focus of an international health response as infected travellers were repatriated to multiple countries for quarantine and treatment.

Before medical evacuations began, the vessel was held under quarantine off the coast of Cabo Verde while authorities assessed the extent of the outbreak. Despite mounting concern surrounding the rare transmission pattern, the WHO previously stated that the overall threat to the wider public remained low while investigations and monitoring efforts continued.

What Is a 'Generation 3' Hantavirus Infection?

Although the WHO states that a wider spread of the hantavirus is unlikely, some observers in the field are concerned about Generation 3 transmissions.

In the context of the May 2026 cruise ship outbreak, the term 'generation' refers to stages of human-to-human transmission involving the Andes strain of hantavirus.

Generation 3 Hantavirus Transmission Sequence

Unlike the Sin Nombre hantavirus strain commonly found in the United States — which primarily spreads through rodent exposure — the Andes strain has previously shown the rare ability to transmit infections between humans through prolonged close contact.

This is how hantavirus, especially the Andes strain, can rapidly spread through populations:

• Generation 1: The original infected patient, believed to be a 70-year-old Dutch man exposed to rodents during travel in Argentina.
• Generation 2: Individuals infected directly by the first patient, including close contacts, family members, or passengers aboard the ship.
• Generation 3: Individuals infected by people in Generation 2 rather than directly from the original source.

Health officials are especially concerned because confirmation of multiple Generation 3 infections would suggest sustained chains of human transmission are occurring beyond the original exposure event.

Andes Hantavirus Incubation Period

As investigators race to determine whether the outbreak has entered a new transmission phase, international monitoring efforts continue to expand. Public health agencies are urging recent passengers, crew members, and contacts to immediately report symptoms, including fever, muscle pain, breathing difficulties, and fatigue.

More significantly, health organisations are closely watching for signs of a possible 'Generation 3' infection — a development that could indicate the virus is continuing to spread from human to human beyond the original cluster aboard the MV Hondius.

The Andes virus (ANDV), which is the hantavirus strain that struck MV Hondius, has an incubation period of one to six weeks or 7 to 42 days, with some cases exhibiting symptoms as early as one week and as late as eight weeks following exposure. Symptoms generally appear about 18 days after exposure to the virus.

As of 13 May, only Generation 2 infections are occurring. In about 7 to 42 days from now, it will be evident if the virus has spread to Generation 3 patients – people who were not on the cruise ship but became ill after coming in contact with infected passengers from the MV Hondius.