What to know about hantavirus, the illness suspected in a cruise ship outbreak

A rodent-borne illness is suspected of causing an outbreak aboard a cruise ship that has killed three people and sickened others.

The germ, called hantavirus, has been confirmed in one of the cases. The World Health Organization said detailed investigations of the cruise ship outbreak are ongoing, including further laboratory testing.

Disease outbreaks involving gastrointestinal and respiratory illnesses happen periodically on cruise ships, which are full of people in close quarters for long stretches of time. They are usually caused by germs that are highly contagious — most notably, norovirus.

There were 23 gastrointestinal outbreaks on cruise ships that called at U.S. ports last year, with 18 caused by norovirus, according to the U.S. Centers for Disease Control and Prevention.

But hantavirus is not typically associated with cruise ships, and it is not easily spread between people.

Studies indicate hantaviruses have been around for centuries, with outbreaks documented in Asia and Europe. It wasn’t until the early 1990s that a previously unknown group of hantaviruses emerged in the southwestern United States as the cause of an acute respiratory disease now known as hantavirus pulmonary syndrome.

The disease gained attention last year after late actor Gene Hackman ’s wife, Betsy Arakawa, died from a hantavirus infection in New Mexico.

The virus is spread by rodents and, more rarely, people

Hantavirus is mainly spread by contact with rodents or their urine, saliva or droppings, particularly when the material is disturbed and becomes airborne, posing a risk of inhalation. People are typically exposed to hantavirus around their homes, cabins or sheds, especially when cleaning out enclosed spaces with little ventilation or exploring areas where there are mouse droppings.

The WHO says that while it rarely happens, hantaviruses can also spread directly between people.

There’s one strain endemic to Argentina and Chile that does have the ability to transmit person-to-person, said Steven Bradfute, an associate professor and associate director of the Center for Global Health at the University of New Mexico Health Sciences Center, which specializes in hantavirus research.

If it is what is known as Andes virus, he said it’s typically fairly contained because it would spread only through close contact, such as sharing a bed or sharing food — unlike like the common cold or influenza.

“We haven’t had huge person-to-person spreads of hantavirus infection ever before and there’s no reason to suspect a huge outbreak from this case at this point,” Bradfute said.

The U.S. CDC began tracking the virus after a 1993 outbreak in the Four Corners region — the area where Arizona, Colorado, New Mexico and Utah meet.

It was an astute physician with the Indian Health Service who first noticed a pattern of deaths among young patients, said Michelle Harkins, a pulmonologist with the University of New Mexico Health Sciences Center who for years has been studying the disease and helping patients.

Most U.S. cases are in Western states. New Mexico and Arizona are hot spots, likely because the odds are greater for mouse-human encounters in rural areas.

The illness starts with flu-like symptoms

An infection can rapidly progress and become life-threatening. Experts say it can start with symptoms that include a fever, chills, muscle aches and maybe a headache — much like the flu would feel.

Symptoms of hantavirus pulmonary syndrome usually show between one and eight weeks after contact with an infected rodent. As the infection progresses, patients might experience tightness in the chest, as the lungs fill with fluid.

The other syndrome caused by hantavirus -- known as hemorrhagic fever with renal syndrome, which can cause bleeding, high fever, and kidney failure -- usually develops within a week or two after exposure.

Death rates vary by which hantavirus causes the illness. Hantavirus pulmonary syndrome is fatal in about 35% of people infected, while the death rate for hemorrhagic fever with renal syndrome varies from 1% to 15% of patients, according to the CDC.

A lot of unknowns about the illness and treatment

There is no specific treatment or cure, but early medical attention can increase the chance of survival.

Despite years of research, many questions have yet to be answered, including why it can be mild for some people and severe for others and how antibodies are developed. Some researchers have been following patients over long periods of time in hopes of finding a treatment.

“In the Americas, hantavirus infection is very serious, but it’s also quite rare,” Bradfute said, “and so for a time that probably led to less research into it because of funding priorities, but I know there’s been a lot of interest in funding hantavirus work of late.”

While there are “a lot of mysteries,” Harkins noted that what researchers do know is that rodent exposure is key.

The best way to avoid the germ is to minimize contact with rodents and their droppings. Use protective gloves and a bleach solution for cleaning up rodent droppings. Public health experts caution against sweeping or vacuuming, which can cause virus particles to get into the air.

Different versions of hantavirus documented in different countries

The word hantavirus refers to a broad family of viruses, with different versions in different countries. Almost none of them have been found to spread from person to person, with the possible exception of a version found in South America — and it makes sense that virus is under suspicion, since the cruise originated in Argentina, said Angela Luis, a hantavirus researcher at the University of Montana.

A thorough investigation will be crucial in determining exactly what happened, and may help settle the question of whether it does spread among people, Luis said.

“My guess is we’re going to learn a lot from this,” Luis said.

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Associated Press medical writer Mike Stobbe contributed from New York.