What is hantavirus? How it spreads, symptoms and risks

A suspected outbreak of a rodent-borne illness on a cruise ship, which has resulted in three deaths and several people falling ill, has brought attention to a little-known virus called hantavirus. While one case has already been confirmed, the World Health Organisation has said that detailed investigations, including further laboratory testing, are still ongoing.

Why this outbreak is unusual

Illness outbreaks on cruise ships are not uncommon. These are often linked to gastrointestinal or respiratory infections, largely because people stay in close quarters for extended periods. Highly contagious viruses such as Norovirus are usually responsible.

Data from the US Centers for Disease Control and Prevention shows that there were 23 gastrointestinal outbreaks on cruise ships that docked at US ports last year, and 18 of these were caused by norovirus.

However, hantavirus is not typically linked to cruise ship outbreaks and does not spread easily from person to person, making this situation unusual.

A virus with a long history

Research suggests that hantaviruses have existed for centuries, with outbreaks recorded across parts of Asia and Europe. It was only in the early 1990s that a new group of hantaviruses was identified in the southwestern United States. This group was found to cause a severe lung condition now known as Hantavirus Pulmonary Syndrome.

The illness gained wider attention last year after the death of Betsy Arakawa, wife of actor Gene Hackman, who died from a hantavirus infection in New Mexico.

How hantavirus spreads

Hantavirus mainly spreads through contact with rodents or their bodily waste, including urine, saliva and droppings. The risk increases when these materials are disturbed and become airborne, making them easy to inhale.

People are often exposed in everyday settings such as homes, cabins or sheds, especially when cleaning enclosed or poorly ventilated areas where rodent droppings may be present.

WHO notes that although it is rare, some forms of hantavirus can spread directly between people.

One such strain, known as the Andes virus, is found in parts of Argentina and Chile and can transmit from person to person. According to Steven Bradfute, an associate professor at the University of New Mexico Health Sciences Center, such transmission usually requires close contact, such as sharing food or sleeping arrangements. It does not spread as easily as common illnesses like the cold or flu.

Bradfute also pointed out that large-scale person-to-person outbreaks of hantavirus have not been recorded so far, and there is no immediate reason to expect one in this case.

Where it has been seen before

The US Centers for Disease Control and Prevention began closely tracking hantavirus after an outbreak in 1993 in the Four Corners region, where Arizona, Colorado, New Mexico and Utah meet.

The initial pattern of illness was noticed by a doctor working with the Indian Health Service, according to Michelle Harkins, a lung specialist who has studied the disease for years.

Most cases in the United States are reported in western states, particularly New Mexico and Arizona. This is likely due to greater chances of contact between humans and rodents in rural areas.

Symptoms to watch for

Hantavirus infection often begins with symptoms that feel similar to the flu. These can include fever, chills, muscle aches and headaches.

For hantavirus pulmonary syndrome, symptoms usually appear between one and eight weeks after exposure to infected rodents. As the illness progresses, patients may develop chest tightness as fluid builds up in the lungs.

Another illness linked to hantavirus is Hemorrhagic Fever with Renal Syndrome, which can cause bleeding, high fever and kidney failure. This form usually develops within one to two weeks after exposure.

How serious is it?

The severity of the disease depends on the specific strain of hantavirus involved. According to the US Centers for Disease Control and Prevention, hantavirus pulmonary syndrome has a fatality rate of about 35 percent.

For hemorrhagic fever with renal syndrome, the death rate ranges from 1 per cent to 15 percent.

Treatment and what we still do not know

There is currently no specific cure or targeted treatment for hantavirus infection. However, early medical care can improve a patient’s chances of survival.

Despite ongoing research, many aspects of the illness remain unclear. Experts are still trying to understand why some people experience mild symptoms while others develop severe disease, as well as how the body builds immunity.

Bradfute noted that although hantavirus infections in the Americas are serious, they are also quite rare. This may have limited research funding in the past, though interest in studying the virus has grown in recent years.

How to reduce risk

Health experts agree that the best way to prevent infection is to avoid contact with rodents and their droppings.

When cleaning areas that may be contaminated, it is recommended to wear protective gloves and use a bleach solution. Sweeping or vacuuming should be avoided, as this can release virus particles into the air.

Different types across the world

Hantavirus is not a single virus but a group of related viruses found in different parts of the world. Most of these do not spread between people. The exception may be certain strains in South America.

Experts believe this is relevant to the current cruise ship case, as the voyage began in Argentina. Angela Luis, a researcher at the University of Montana, noted that this could explain why hantavirus is being closely examined in the investigation.

She added that a detailed inquiry into the outbreak will be important to understand exactly what happened and to determine whether human-to-human transmission played any role.