Hantavirus explained: How deadly is it? How contagious is it? Should you be worried?

Hantavirus on cruise ship: The first day of evacuations from the cruise ship at the centre of the hantavirus outbreak has concluded, with 94 passengers from 19 nationalities evacuated, according to Spanish health authorities.

Hantavirus Outbreak on Cruise Ship MV Hondius: Cases, Deaths and What Comes Next

A hantavirus outbreak linked to the expedition cruise ship MV Hondius has prompted emergency evacuations, multi-country contact tracing and a formal response from the World Health Organization (WHO), after six confirmed cases and three deaths were recorded among people connected to the vessel. Health authorities across Europe, South Africa and beyond are now working to identify everyone who may have been exposed.

The MV Hondius arrived at the Spanish island of Tenerife on Sunday morning carrying 147 people. By the end of the day, 94 passengers had been evacuated in a carefully managed repatriation operation that Spain's health minister, Monica Garcia, described as having gone "according to plan" at a press conference held at the port.

What Is Hantavirus?

Hantavirus is a rare but exceptionally dangerous pathogen typically transmitted to humans through contact with infected rodents, their droppings or their saliva. It is not a new virus, but outbreaks remain uncommon, and the strain now linked to the MV Hondius has placed it under sharper global scrutiny than it has received in years.

The strain confirmed in this outbreak is the Andes hantavirus, first identified in South America and considered endemic to parts of Argentina and Chile. It is the only known strain of hantavirus with documented capacity for human-to-human transmission, which distinguishes this cluster from more typical cases and has prompted the scale of international response now underway.

WHO has classified hantaviruses as an emerging priority pathogen, a designation that reflects both the severity of the disease and the limited treatment options available.

How Contagious Is Hantavirus?

For most strains of hantavirus, human-to-human transmission does not occur. The Andes strain is the exception, though even here, spread between people remains rare and requires specific conditions.

WHO says that human-to-human transmission has been observed in community settings involving close and prolonged contact, such as among married couples or individuals sharing sleeping quarters. It is not airborne like influenza or COVID-19, according to the WHO.

"This is not a virus that spreads like flu or like Covid. It's quite different," Dr Maria Van Kerkhove, WHO's director for epidemic and pandemic preparedness and prevention, told CNN.

Peak infectiousness is believed to coincide with the day a fever first appears.

In a study of a 2018 to 2019 outbreak in Argentina, Palacios found that before any public health interventions, each infected person passed the virus to an average of 2.12 others. That figure dropped to 0.96 once isolation and quarantine measures were introduced, bringing transmission below the threshold needed for sustained spread. Roughly 3,000 cases of the Andes strain have ever been recorded in history, according to Palacios.

The European Centre for Disease Prevention and Control (ECDC) has classified everyone aboard the MV Hondius as a close contact, given the enclosed environment and shared activities on the vessel.

How Deadly Is Hantavirus?

The mortality figures are stark. The Americas' strain of hantavirus can cause hantavirus pulmonary syndrome, a severe respiratory illness, and approximately 38% of people who develop respiratory symptoms may die, according to the ECDC.

Three people connected to the MV Hondius have already died: a 70-year-old Dutch man, his 69-year-old wife and a German woman, all of whom developed symptoms between early and late April. A fourth patient, a male passenger evacuated to South Africa, remains in intensive care.

According to the WHO, there is no vaccine to prevent hantavirus infection. There is no specific antiviral treatment for it either. The only tools available to clinicians are supportive, meaning managing symptoms, maintaining oxygen levels and preventing organ failure. WHO advises that early supportive care and prompt referral to a facility with a fully equipped intensive care unit can improve the chances of survival.

The absence of any targeted medical intervention means that early detection and rapid hospitalisation are the most decisive factors in whether a patient lives or dies.

How Long Does It Take for Hantavirus Symptoms to Appear?

Hantavirus typically incubates for one to six weeks after exposure, though the WHO notes that symptoms can appear as early as one week or as late as eight weeks after initial contact with the virus.

Early symptoms broadly resemble those of influenza: fever, fatigue, headache, muscle aches and sometimes gastrointestinal problems. In cases that progress to hantavirus pulmonary syndrome, patients develop shortness of breath and fluid in the lungs, which can deteriorate rapidly.

WHO advises that all passengers and crew from the MV Hondius remain vigilant for hantavirus symptoms for 45 days from their last possible exposure.

Timeline: How the Hantavirus Outbreak Unfolded Aboard MV Hondius

The first passenger is believed to have developed symptoms on 6 April. A 70-year-old Dutch man fell ill with fever, headache, abdominal pain and diarrhoea. He went into respiratory distress on 11 April and died aboard the ship that day. Because no microbiological tests were performed at the time, he is classified as a probable rather than confirmed case.

His 69-year-old wife went ashore at Saint Helena on 24 April with stomach problems, then flew to Johannesburg, where her condition worsened. She collapsed whilst attempting to board a flight home to the Netherlands and died at a nearby hospital on 26 April. Molecular testing on 4 May confirmed she had hantavirus.

A German woman developed fever and malaise on 28 April, contracted pneumonia and died on 2 May aboard the ship. Post-mortem testing in the Netherlands confirmed the Andes strain.

The last person to develop symptoms did so on 28 April.

Who Has Been Infected and Where Are They Now?

As of Friday, the WHO reported six confirmed cases and two suspected cases. Among those confirmed:

A male passenger reported to the ship's doctor on 24 April with fever, shortness of breath and signs of pneumonia. He was evacuated to South Africa on 27 April and remains in intensive care. Molecular testing on 2 May confirmed Andes hantavirus.

The ship's doctor developed symptoms on 30 April, tested positive on 6 May and was evacuated to the Netherlands, where he is stable in isolation.

A ship guide reported mild respiratory and gastrointestinal symptoms on 27 April, tested positive on 6 May and was also evacuated to the Netherlands, where he is stable.

A passenger who disembarked at Saint Helena on 22 April and returned to Switzerland via South Africa and Qatar developed symptoms on 1 May, isolated himself, reported to local health authorities and tested positive on 5 May. He is in isolation in a Swiss hospital.

A man who left the ship at Tristan da Cunha on 14 April is considered a probable case. His symptoms began on 28 April, and he is stable in isolation.

The Indian embassy in Spain confirmed on Sunday that two Indian nationals aboard the vessel, both travelling as crew members, are "healthy and asymptomatic" and have been evacuated to the Netherlands.

Where Did the Hantavirus Come From?

Authorities are still investigating the precise origin of the cluster. WHO believes the Dutch couple and possibly others were infected before boarding the cruise on 1 April, most likely during activities in Argentina, where the Andes strain is endemic.

"WHO believes that the Dutch couple and possibly others were infected before they joined the cruise on April 1, possibly while doing some activities in Argentina, where hantavirus is endemic," Van Kerkhove said.

How Many People Were Potentially Exposed to the Hantavirus?

As of Friday, 147 people were aboard the MV Hondius, comprising 87 passengers and 60 crew members from 24 nationalities. Authorities are additionally tracing 82 passengers and six crew members from an Airlink flight from Saint Helena to Johannesburg on 25 April, which the Dutch woman took before she died.

KLM confirmed that Dutch authorities have also contacted an undisclosed number of passengers from a second flight, the woman briefly boarded in Johannesburg before disembarking because she was too ill to travel. A flight attendant who experienced symptoms subsequently tested negative, according to the WHO.