Health experts suspect a disease carried by rodents, known as hantavirus, is behind an outbreak on a cruise ship that has killed three people and left several others ill.
Research shows hantaviruses have existed for centuries, with past outbreaks reported in Asia and Europe. In those regions, the virus has been linked to hemorrhagic fever and kidney failure. In the early 1990s, a new group of hantaviruses was identified in the southwestern United States, causing a serious lung condition now called hantavirus pulmonary syndrome.
The disease drew wider attention last year after Gene Hackman’s wife, Betsy Arakawa, died from a hantavirus infection in New Mexico.
The World Health Organization said Sunday that investigations into the cruise ship outbreak are ongoing. These include lab testing, epidemiological studies and genetic sequencing of the virus.
Hantavirus mainly spreads through contact with rodents or their urine, saliva and droppings. The risk increases when these materials are disturbed and become airborne, making it easier to inhale the virus. People are often exposed while cleaning enclosed spaces such as homes, cabins or sheds, especially where rodent droppings are present.
Although rare, the WHO says the virus can also spread directly from person to person.
The Centers for Disease Control and Prevention began monitoring the disease after a 1993 outbreak in the Four Corners region of the United States. Most cases in the country are reported in western states, particularly New Mexico and Arizona, where human contact with rodents is more common in rural areas.
The illness usually begins with flu-like symptoms such as fever, chills, muscle pain and headaches. Experts say it can be difficult to distinguish from the flu in the early stages. Symptoms typically appear one to eight weeks after exposure.
As the disease worsens, patients may develop chest tightness as fluid builds up in the lungs. Another form of the disease, which affects the kidneys, can develop within one to two weeks after exposure.
Fatality rates vary depending on the type of hantavirus. The lung-related form has a death rate of about 35%, while the kidney-related form ranges from 1% to 15%, according to the CDC.
There is no specific cure or treatment, but early medical care can improve survival chances. Researchers say many aspects of the disease remain unclear, including why symptoms can be mild in some people but severe in others.
Health experts advise reducing contact with rodents and their droppings to lower the risk. When cleaning contaminated areas, they recommend using gloves and disinfectants such as bleach, and avoiding sweeping or vacuuming, which can spread the virus into the air.