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

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

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

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

Health officials said that the risk to the public posed by the disease is low, and that cases are typically only found in West Africa.

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

What is Lassa fever?

Lassa fever is "an acute viral hemorrhagic illness caused by Lassa virus," according to the World Health Organization.

"Lassa fever is a potentially life-threatening viral disease," Dr. Albert Ko, the Raj and Indra Nooyi professor of public health at the Yale School of Public Health, told ABC News. "The virus, which is in this class of family called arenaviruses, is harbored by rats, and rats specifically in the western part of Africa."

The virus is primarily spread by multimammate rats belonging to the genus Mastomys, according to the CDC.

Only multimammate rats in Western African countries – such as Guinea, Liberia, Nigeria and Sierra Leone – are known to carry the virus. However, people who live in neighboring countries are also at risk of infection with the Lassa virus.

The first documented case was identified in 1969 in Lassa, Nigeria, which gave the illness its name, the CDC said.

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

How is Lassa fever spread?

Lassa fever is often spread by coming into contact with the urine or droppings of contaminated rats. Multimammate rats often live in areas where food supplies are stored. Such contact can occur by touching contaminated objects, eating contaminated food, getting the virus in an open cut or sore, eating infected rodents, or breathing air that's contaminated with infected urine or droppings, such as when cleaning or sweeping, the CDC said.

Lassa fever can also be spread from person to person by coming into contact with an infected person's blood or bodily fluids, or through sexual contact.

"It's not airborne. It's not like COVID," Dr Robert Murphy, a professor of infectious diseases at the Northwestern University Feinberg School of Medicine, told ABC News. "[Lassa fever], it has to be a fluid. … So, you don't have to worry about being in the same room with somebody, but you have to be worried if you have been touching that person or dealing with that person and being exposed to any fluids that they have."

What are the symptoms of Lassa fever?

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

About eight in 10 people who contract Lassa fever have mild symptoms, including slight fever, tiredness, weakness and headaches, or they experience no symptoms at all and are never diagnosed, the CDC said. The remaining 20% will experience serious symptoms that can include bleeding, facial swelling and vomiting, as well as pain in the chest, back and abdomen, difficulty breathing, and shock.

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

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

"Once they get really sick, the death is pretty quick. It's within seven to 14 days, usually," Murphy said.

He added that diagnosing Lassa fever can be challenging, because it isn't routine to test for the virus. Those people handling samples need to be careful in case they come into contact with it and become infected, Murphy said.

How is Lassa fever treated?

Patients who are ill with Lassa fever can receive an antiviral drug called Ribavirin. It's most successful when given to patient soon after they become sick and show symptoms, according to the CDC.

Supportive care, including rest, hydration and treating the virus' symptoms, is also recommended.

Tips for preventing Lassa fever

There are currently no vaccines to prevent becoming infected with the Lassa virus.

If someone is traveling to West Africa, the CDC says the primary method of preventing infection with Lassa fever is to stay away from rats.

The CDC further recommends storing food in rat-proof containers and keeping one's home clean. One should also avoid eating rats, and should trap and dispose of any rats in and around homes.

That said, most Americans don't need to be concerned about Lassa fever, said Yale School of Public Health's Dr. Ko.

"This is a disease which is really an important public health problem but it's localized to Western Africa," he said. "It's not a disease that is easily spread from one place to another, unlike some of the other diseases that we've faced, such as Zika and COVID, and that's because people usually are not infectious until they start developing symptoms, and many times we can screen and know people who are sick, you know, identify them and isolate them before they start traveling."