Hantavirus: More cases 'likely', no sign of a global wave — WHO

Dozens of passengers from the cruise ship MV Hondius are now under medical monitoring, as health authorities describe the hantavirus situation as "contained" but fragile.

Before the mass evacuations, a contact-tracing "gap" in St. Helena has complicated the global response.

The next several days are critical: will this remain a limited cluster or evolve into a broader international health incident?

• The WHO says hantavirus is serious but not yet a widening global outbreak.

• A contact-tracing gap in St. Helena complicates the global response.

• Confirmed cases tied to the ship have appeared in the US and France.

• One French patient is in deteriorating condition.

• 18 evacuees are under strict monitoring in Nebraska and Atlanta.

• Nine US states are tracing potential secondary exposures.

A 'worsening' case in France

On Monday, a French passenger tested positive for the virus. France’s health minister, Stéphanie Rist, said the patient’s condition was deteriorating, heightening concern that some infections linked to the ship may turn severe.

WHO: more cases 'likely', but no sign of a global wave

Also Monday, Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, cautioned that while additional cases are expected to surface, there is “no sign we are seeing the start of a larger outbreak.”

He stressed the WHO’s limits in compelling compliance: countries can be advised on hantavirus protocols, but not forced to adopt them.

What we know now

According to health officials:

97 contacts had been linked to the cruise ship hantavirus cases, according to South African health authorities

16 people are being monitored at the University of Nebraska Medical Center (UNMC) in Omaha.

15 US evacuees are housed in the quarantine unit — a hotel-style facility for people without symptoms.

1 person, who tested positive but has no symptoms, is in UNMC’s "biocontainment" unit, a hospital-grade isolation ward used for high-risk pathogens.

2 passengers are at Emory University Hospital in Atlanta.

• One had mild symptoms and was placed in biocontainment but tested negative on Tuesday.

• The other is a close contact under observation.

Those brought to the US include 17 Americans and one British dual national evacuated from the vessel on Sunday.

1993: The respiratory ailment caused by hantavirus was first identified in the "Four Corners" region of the US Southwest in 1993. The disease has been found to be transmitted to humans from deer mice, either through contact with urine, droppings, saliva or nesting materials of infected rodents or by inhaling dust contaminated with the virus.

'St. Helena gap': passengers dispersed without tracing

A major concern for global health authorities is that passengers disembarked on April 24 onto the island of Saint Helena, an island in the South Atlantic Ocean [known historically as the place of Napoleon Bonaparte's final exile.], without formal contact tracing.

From there, travelers dispersed internationally, prompting at least a dozen countries to begin retroactive monitoring.

• 2 Dutch people from the ship died from the virus; a third has been confirmed to have contracted it.

• A Dutch couple who had travelled around South America before boarding the ship in Ushuaia, Argentina on April 1 were the first fatalities.

• The husband, 70, showed symptoms on April 6 and died on April 11. His body was taken off the ship during its April 22-24 call at Saint Helena island in the south Atlantic.

• No hantavirus test was carried out and he is considered a "probable case", according to the WHO.

• His wife, 69, also left the ship at Saint Helena, feeling "unwell".

• Her health deteriorated during an April 25 flight to Johannesburg; she died in hospital a day later, hantavirus was confirmed on May 4.

• Third Dutch case: The ship's doctor reported symptoms on April 30. A test showed him positive for the Andes strain of the virus on May 6.

Nine US states now monitoring possible exposures

Health departments across the US are tracing and monitoring residents who may have had secondary contact with infected passengers. So far, no cases have been confirmed in these states:

• Arizona

• California

• Georgia

• Kansas

• Maryland

• New Jersey

• Texas

• Virginia

• Washington

In November 2024, five people were reportedly stricken with the rare, rodent-borne hantavirus illness in Washington state (since February 2024), three of whom have died. It was the state's worst outbreak of the disease in at least 18 years (till then), public health officials said, as per AFP. The three fatal cases also mark the highest death toll from hantavirus pulmonary syndrome in Washington state during a single year.

Kansas: 3 'high-risk exposure' contacts

The Kansas Department of Health and Environment says three people are being monitored after prolonged close contact overseas with an individual from the ship who later tested positive. None show symptoms and are not considered contagious.

Washington: Flight exposure and 1 UNMC patient

Washington health officials say:

• Two Seattle-area residents were briefly on a flight with a passenger who later tested positive. They are asymptomatic.

• A third Washington resident, from King County, is among those quarantined at UNMC in Omaha.

Why authorities are taking no chances

Hantaviruses are typically spread through contact with infected rodent droppings, urine, or saliva.

Human-to-human transmission is rare, but certain strains — such as the Andes strain previously documented in South America — have shown that it is possible under close conditions.

The cruise ship’s confined environment, shared ventilation, and prolonged contact among passengers created a scenario where health experts fear unusual transmission patterns may have occurred.

That is why patients without symptoms are still being housed in biocontainment-grade facilities and why states are aggressively monitoring even indirect contacts like seatmates on commercial flights.