Three people have died in a hantavirus outbreak on a luxury cruise ship, with another four confirmed or suspected cases.

What exactly is hantavirus, and what are the implications of its spread for global public health?

What is it?

Hantaviruses are rodent-borne viruses that can infect people and cause illness. The World Health Organization estimates there are 10,000 to 100,000 human cases globally each year, with severity varying by strain.

How is the virus spread?

Hantavirus spreads primarily through rodents, infecting people via contact with rats or mice, or their urine, droppings, or saliva — often when the virus becomes airborne during cleaning of infested areas.

Less commonly, it spreads through contaminated surfaces.

The Andes strain of hantavirus, found largely in Argentina and Chile, is the only known variant that can spread through close, prolonged human-to-human contact.

While WHO believes this strain is responsible for the infections on the cruise ship, this has not been confirmed.

What are the symptoms of infection?

Hantaviruses in different parts of the world cause varying symptoms or diseases, and some cause none at all.

Symptoms typically begin one to eight weeks after exposure and may include fever, muscle aches, and gastrointestinal issues, according to WHO.

In Europe and Asia, hantaviruses have been known to cause hemorrhagic fever with renal syndrome, which mainly affects the kidneys and blood vessels.

In the Americas, infection can cause hantavirus cardiopulmonary syndrome, which progresses quickly and leads to fluid buildup in the lungs along with heart complications.

Fatality rates for hantavirus cardiopulmonary syndrome can reach up to 50%, WHO says, compared with 1% to 15% for infections more common in Asia and Europe.

Can hantavirus infection be treated?

There is no specific treatment for hantavirus infection, so care focuses on supportive measures, including rest and fluids. Patients may require breathing support, such as a ventilator.

Prevention centers on limiting contact with rodents through measures such as keeping areas and surfaces clean.

During outbreaks, contact tracing can help those potentially exposed access hospital care earlier, improving outcomes and reducing further spread.

What are the risks to the general public?

The cruise ship outbreak is unusual and under investigation by WHO and several countries, but the risk to the public remains low, the agency says.

More broadly, WHO’s Americas branch warned in December that hantavirus infections were rising in the region, particularly in Bolivia and Paraguay. Brazil and Argentina – which has the most cases – have also seen increasing lethality.

Argentina reported 21 deaths last year, a 32% fatality rate among 66 people who contracted hantavirus pulmonary syndrome, compared with a 15% average over the past four years. – Rappler.com