A deadly virus outbreak aboard a remote expedition cruise has begun spilling beyond the ship, and with passengers now back in multiple countries, reportedly including Australia, questions are mounting over whether the threat could spread further.

At the centre of concern is hantavirus, a rare but potentially fatal disease with a mortality rate of up to 40 per cent.

While typically spread through contact with rodent droppings, health authorities believe this particular outbreak may involve a strain capable of human-to-human transmission, raising the stakes significantly.

The outbreak began aboard the MV Hondius, a Dutch-operated expedition vessel travelling through South America. The cruise, which set sail from Ushuaia in Argentina on April 1 destined for Cape Verde, counted 88 passengers and 59 crew members, with 23 nationalities onboard.

Since then, at least three passengers have died, and several others have fallen seriously ill, with the ship now anchored off Cape Verde as authorities attempt to contain the situation.

But the bigger concern may lie beyond the vessel itself.

How many people have been exposed?

At least 23 passengers disembarked during a scheduled stop at Saint Helena in April, unaware they had potentially been exposed to the virus, and have since returned home to countries around the world, including Australia.

“There are 23 people wandering around there, and until three days ago, no one had contacted them,” a passenger still aboard the ship told Spanish newspaper El Pais.

“The Australian went back to Australia, the one from Taiwan to Taiwan, the Americans to all corners of North America. The Englishman to England, the Dutch to their homes… I don’t remember the rest.”

“The Department of Foreign Affairs and Trade is aware of four Australians aboard the MV Hondius,” DFAT told The Nightly.

“DFAT is not aware of any Australians affected by the reported hantavirus outbreak. Owing to privacy obligations we are unable to comment further.

“DFAT stands ready to provide consular assistance if required.”

Swiss health authorities confirmed that one returning passenger has tested positive for hantavirus after arriving home from the cruise. The man initially tested negative before later revealing a confirmed diagnosis, highlighting concerns around the virus’s incubation period, which can stretch up to eight weeks.

That delay has complicated international efforts to track and contain the outbreak.

“International contact tracing is ongoing. Passengers who disembarked from the ship were informed of the hantavirus case by the ships’ operators and asked to report any signs and symptoms,” a World Health Organisation representative said.

“Working with national authorities and the ship’s operators, our teams have built a list of who was where when, in order to ensure that any potential exposure is documented and people can get help if they develop symptoms,” the rep said.

“This contact tracing also helps to contain any potential spread.”

Oceanwide Expeditions continues to provide updates on the evolving crisis, “The first of two medicalised aircraft, carrying two of the three individuals transferred from m/v Hondius earlier today has landed in the Netherlands. The two individuals on board have been received by specialist medical and screening teams. The second medicalised aircraft carrying the third individual is currently experiencing a delay.”

Investigators now believe the outbreak may have originated from a couple who boarded the ship after visiting a landfill site in Ushuaia, Argentina, to take part in birdwatching, where they may have been exposed to infected rodents. Both later died.

The suspected strain, known as the Andes virus, is particularly concerning due to its rare ability to spread between humans, a factor that has prompted urgent international monitoring.

Still, health officials have been quick to stress that the overall risk of widespread transmission remains low.

Despite the dramatic scenes, including emergency evacuations of infected passengers and growing political concern in parts of Europe, authorities say hantavirus does not spread as easily as more common respiratory illnesses.

Symptoms

HPS is a severe and potentially deadly disease that affects the lungs. Symptoms of HPS usually start to show 1 to 8 weeks after contact with an infected rodent, the Centres for Disease Control and Prevention reported.

Early Symptoms (Flu-like)

• Fever and chills.
• Fatigue and muscle aches (particularly in large muscle groups).
• Headaches and dizziness.
• Gastrointestinal issues: nausea, vomiting, diarrhea, and abdominal pain.

Late Symptoms (Progressive, Pulmonary Syndrome)

• Severe coughing.
• Tightness in the chest.
• Shortness of breath.
• Rapidly worsening breathing difficulties (described as feeling like “fluid in the lungs”)

Should Australians be concerned?

For Australians, the key risk factor is proximity.

While at least one passenger has reportedly returned to Australia, there is currently no indication of local transmission. Most cases remain linked to direct exposure or close contact, and symptoms typically require significant incubation time before emerging.

Even so, the delayed response in notifying passengers has drawn criticism.

“We were in touch with them and kept asking ourselves, ‘When are they going to tell them something?’ Some people weren’t contacted until yesterday,” the onboard passenger said.

As global contact tracing efforts ramp up, the focus now is on identifying anyone who may have been exposed and ensuring they are monitored before symptoms develop.

For now, experts say Australians should remain alert, but not alarmed.

The outbreak is serious, but contained, and while the virus has crossed borders, it has not yet taken hold beyond isolated cases.