What to know about Lassa fever after an Iowa resident dies from the rare disease

An Iowa resident has died after contracting suspected Lassa fever, health officials said.

According to the Centers for Disease Control and Prevention (CDC) and the Iowa Department of Health and Human Services (IDHHS), the patient was diagnosed on Tuesday after returning to the United States from West Africa earlier this month.

The patient was admitted to the University of Iowa Health Care Medical Center in Iowa City in isolation and died Tuesday afternoon, according to officials.

Health officials said the risk posed by the disease to the public was low and that cases typically occur only in West Africa.

Here's what you need to know about Lassa fever, how it spreads, and how to treat it:

What is Lassa fever?

According to the World Health Organization, Lassa fever is “an acute viral hemorrhagic disease caused by Lassa virus.”

“Lassa fever is a potentially life-threatening viral disease,” said Dr. Albert Ko, Raj and Indra Nooyi Professor of Public Health at the Yale School of Public Health, told ABC News. “The virus, which belongs to this class of arenaviruses, is transmitted by rats, particularly in the western part of Africa.”

According to the CDC, the virus is spread primarily by multimammary rats of the genus Mastomys.

Only multiracial rats in West African countries – such as Guinea, Liberia, Nigeria and Sierra Leone – are known to transmit the virus. But people who live in neighboring countries are also at risk of becoming infected with the Lassa virus.

The first documented case was identified in Lassa, Nigeria, in 1969, giving the disease its name, the CDC said.

In the past 55 years, there have only been eight travel-related cases of Lassa fever in the U.S., according to IDHHS, making its occurrence in the U.S. very rare.

How does Lassa fever spread?

Lassa fever is often transmitted through contact with the urine or feces of infected rats. Multimamma rats often live in areas where food supplies are stored. Such contact can occur through touching contaminated objects, eating contaminated food, contracting the virus in an open cut or wound, eating infected rodents, or inhaling air contaminated with infected urine or feces, such as while cleaning or sweeping, according to the CDC.

Lassa fever can also be spread from person to person through contact with the blood or body fluids of an infected person or through sexual contact.

“It is not airborne. It’s not like COVID,” said Dr. Robert Murphy, professor of infectious diseases at Northwestern University Feinberg School of Medicine, told ABC News. “(Lassa fever), it must be a liquid. …So you don't have to worry if you're in the same room with someone, but you do have to worry if you touch that person or have anything to do with that person and being exposed to any liquids that they have.

What are the symptoms of Lassa fever?

According to the CDC, Lassa fever symptoms typically appear one to three weeks after a person is first infected.

About eight in 10 people who become infected with Lassa fever have mild symptoms, including a low-grade fever, fatigue, weakness and headache, or they experience no symptoms at all and are never diagnosed, according to the CDC. The remaining 20% ​​experience serious symptoms, which may include bleeding, facial swelling, and vomiting, as well as chest, back, and abdominal pain, difficulty breathing, and shock.

Complications can include hearing loss and acute kidney failure, the experts said. If a pregnant person is infected, there is a high risk of miscarriage, as about 95% of fetuses do not survive, according to the CDC.

Less than 1% of people who get Lassa fever die. However, the mortality rate for those who become seriously ill and are hospitalized is around 15%.

“Once they get really sick, death occurs pretty quickly. Typically this happens within seven to 14 days,” Murphy said.

He added that diagnosing Lassa fever can be challenging because testing for the virus is not routine. People who handle samples need to be careful so they don't come into contact with it and become infected, Murphy said.

How is Lassa fever treated?

Patients suffering from Lassa fever may receive an antiviral medication called ribavirin. According to the CDC, it is most successful when given to the patient shortly after they become ill and show symptoms.

Supportive care, including rest, hydration, and treatment of viral symptoms, is also recommended.

Tips for preventing Lassa fever

There are currently no vaccines against infection with the Lassa virus.

If someone travels to West Africa, the most important way to prevent infection with Lassa fever is to stay away from rats, according to the CDC.

The CDC also recommends storing food in rat-proof containers and keeping your home clean. One should also avoid eating rats and catch and dispose of all rats in and around homes.

However, most Americans don't have to worry about Lassa fever, said Dr. Ko from Yale School of Public Health.

“This is a disease that is really a major public health problem but is limited to West Africa,” he said. “Unlike some other diseases we face, like Zika and COVID, it is not a disease that is easily transmitted from one place to another, and that is because people are usually not contagious until they Develop symptoms, and in many cases, we can screen and detect sick people, identify them and isolate them before they go out.”