Hantavirus explained: What it is, how it spreads, and what India needs to know after the cruise ship outbreak

A Dutch expedition cruise ship is at sea with more than 140 passengers and crew from 23 countries. Multiple Hantavirus infections have been linked to the vessel. Three deaths have been associated with the outbreak. Ports initially turned the ship away. The World Health Organization (WHO) deployed an expert on board and arranged diagnostic support for affected countries.

The outbreak has renewed global attention on Hantavirus and its transmission patterns. Here is what Hantavirus is, why the outbreak is unusual, and what experts say India should know about it.

What Is Hantavirus?

Hantaviruses are zoonotic viruses that naturally infect rodents and can occasionally spread to humans. Each virus strain is typically associated with a specific rodent host, in which the virus causes long-term infection without making the animal sick. The virus is shed in rodent urine, droppings, and saliva.

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Humans are usually infected by inhaling contaminated particles, particularly when dried rodent droppings or dust are disturbed during cleaning, farming, forestry work or while staying in rodent-infested spaces. Less commonly, infection can occur through rodent bites. Unlike Covid-19 or influenza, Hantavirus does not spread easily through the air between people and most strains spread only through contact with infected rodents or contaminated environments.

Once inside the body, the virus affects the endothelial cells that line blood vessels, increasing vascular leakage and inflammation. In severe cases affecting the lungs, this can lead to respiratory failure. In other forms of the disease, it can affect the kidneys and blood vessels, causing haemorrhagic fever and renal complications. Outcomes depend on how early patients receive supportive care and how severely the infection progresses.

The disease presents differently across regions. In the Americas, hantavirus can cause Hantavirus cardiopulmonary syndrome (HCPS), a rapidly progressing illness with reported fatality rates of up to 50 per cent in some outbreaks. In Europe and Asia, it more commonly causes haemorrhagic fever with renal syndrome (HFRS), which primarily affects the kidneys and blood vessels and generally has lower fatality rates.

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There is currently no widely licensed vaccine or specific antiviral cure for Hantavirus infections. Treatment is supportive and may include respiratory support, management of cardiac and kidney complications, and intensive care in severe cases. Thousands of Hantavirus infections are reported globally each year, particularly in parts of Asia, Europe and the Americas.

The MV Hondius Outbreak: What Happened?

According to WHO, the MV Hondius departed Ushuaia in southern Argentina on April 1 on a 24-day polar voyage carrying passengers and crew from multiple countries.

The first passenger developed fever, headache, abdominal symptoms and diarrhoea several days into the voyage and later died on board. A second passenger later deteriorated during onward travel and also died after hospitalisation in South Africa. A third death was subsequently linked to the outbreak.

On May 7, WHO said eight cases had been identified, including laboratory-confirmed Hantavirus infections. Several patients were evacuated for treatment and WHO coordinated an international response involving specialists from Europe and public health agencies.

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Speaking at a media briefing, WHO Director-General Tedros Adhanom Ghebreyesus said the first two cases had travelled through Argentina, Chile and Uruguay before boarding the ship, including visits to areas where rodents known to carry Andes virus are present.

“While this is a serious incident, WHO assesses the public health risk as low,” Tedros said. He added that additional cases may still emerge because the incubation period for Andes virus can extend up to six weeks.

The ship is now sailing to the Canary Islands after Spain agreed to receive it. WHO has notified multiple countries whose nationals had disembarked during the voyage.

Why Is the Andes Virus Strain Different?

Nearly all Hantaviruses spread only from rodents to humans. Andes virus, first identified in Argentina in 1995, is the only Hantavirus known to have limited person-to-person transmission.

According to WHO, previous Andes virus outbreaks have shown transmission mainly among household contacts, intimate partners and healthcare providers after prolonged close contact. Public health experts say the close quarters and prolonged exposure aboard the ship may have contributed to transmission in this outbreak.

Health experts say outbreaks involving possible person-to-person transmission on a cruise ship are extremely unusual. Argentina has also reported a rise in Hantavirus infections over the past year, though investigations into the precise source of exposure linked to the ship are continuing. WHO has stated that the outbreak does not currently represent a pandemic threat.

Is Hantavirus Present in India?

India is not considered a high-risk zone for the Andes strain involved in the current outbreak, and no India-linked cases have been reported. The Indian government has not issued any public advisory related to the outbreak.

However, scientific studies over several decades have documented evidence of Hantavirus infections and rodent exposure in India. Researchers and infectious disease experts say the virus may be underdiagnosed because testing and surveillance remain limited.

One of the earliest documented findings came from a 2006 multi-institutional study in Tamil Nadu, where researchers identified evidence of Hantavirus infection among patients with chronic kidney disease, warehouse workers and members of the Irula tribal community, who traditionally engage in rodent trapping. The study identified evidence of Seoul virus, Thailand virus and Hantaan-like virus strains.

In a 2008 commentary published in the Indian Journal of Medical Research, Deepak Gadkari, former director of the National Institute of Virology, Pune, wrote: “The presence of Hantavirus in India has been speculated for several decades.”

A 2012 study among the Irula tribal population in Marakkanam, Tamil Nadu, found Hantavirus seroprevalence among individuals with repeated occupational exposure to rodents.

Research published in 2014 in the Transactions of the Royal Society of Tropical Medicine and Hygiene reported serological evidence of Hantavirus infection among patients presenting with acute febrile illness in India and suggested the disease should be considered in the differential diagnosis of undifferentiated fever cases.

A 2016 case report from Christian Medical College, Vellore described a quarry worker with fever, abdominal symptoms, low platelet count and kidney dysfunction who was later confirmed to have Hantavirus infection. Researchers noted that the disease can resemble conditions such as scrub typhus, leptospirosis and dengue.

A separate rodent surveillance study published in 2017 also documented evidence of Hantaviruses among rodent species in south India and recommended continued monitoring in high-risk populations.

India also has its own Hantavirus-related strain, meaning a virus variant first identified in the country. The Thottapalayam virus was isolated in Tamil Nadu in 1964 from the common house shrew Suncus murinus, making it one of the earliest identified Hantavirus-related isolates in Asia. Its full implications for human disease remain under study.

“Hantavirus might be a rare infection, but it can be severe and progress quickly, making awareness very important,” said Amit Prakash Singh, Consultant - Internal Medicine at the CK Birla Hospital, Delhi. “One major challenge with Hantavirus is that its early symptoms, fever, body aches, fatigue, nausea and headaches often resemble those of common viral illnesses. This similarity can cause delays in diagnosis and treatment.”

Why Experts Say India Needs Better Surveillance

Experts say the larger concern for India is limited awareness, surveillance and testing capacity. Most hospitals do not routinely test for Hantavirus, and specialised laboratory facilities remain limited.

As a result, some infectious disease experts believe sporadic infections may go undetected or be misclassified as dengue, leptospirosis or fever of unknown origin. Because symptoms overlap with dengue, leptospirosis, scrub typhus and viral fever, mild or sporadic Hantavirus infections may go unrecognised.

“The virus mainly spreads through contact with infected rodents, their droppings, urine or saliva especially in poorly ventilated places such as basements, warehouses, barns and storage areas,” Dr Singh said. “Since there is no widely approved vaccine or specific antiviral treatment, prevention is key.”

Public health experts advise avoiding direct contact with rodent droppings, improving ventilation while cleaning closed spaces, and using gloves and masks in heavily rodent-infested environments.

Experts say improving rodent control, expanding diagnostic capacity and increasing clinical awareness in high-risk occupational groups could help strengthen surveillance.