Lassa fever is rare but lethal, and recently claimed 1 life
Key Takeaways
Lassa fever, caused by an arenavirus, is rare in the US, but it recently claimed the life of an individual from the state of Iowa.
Symptoms vary and present similarly to other diseases, making diagnosis difficult, but early treatment is essential.
An individual from Iowa died after contracting a suspected case of Lassa fever, an acute viral hemorrhagic illness. The disease is caused by the Lassa virus, among the family of arenaviruses, and is primarily spread by rats found in West Africa.[][]
Albert Ko, MD, a professor at the Yale School of Public Health, told the media that “Lassa fever is a potentially life-threatening viral disease.”[] Even so, the CDC still considers the risk to the public “extremely low.”[]
The patient had returned to his home in Iowa from West Africa in October 2024 and was hospitalized in isolation, according to the CDC and the Iowa Department of Health and Human Services. Confirmatory testing is planned.[]
Rare in the US
Lassa fever is rare in the US but common in West Africa, where 100,000–300,000 cases and 5,000 related deaths occur each year.[] Since it was first documented in 1969, the US has reported eight travel-associated cases of Lassa fever. If this latest case is confirmed, it will represent the 9th known occurrence in our country.
The virus spreads to humans via contact with infected rodents’ urine or droppings. However, person-to-person transmission occurs via direct contact with a symptomatic individual’s blood or body fluids.[]
“It's not airborne. It's not like COVID,” explained Robert Murphy, MD, a professor of infectious diseases at the Northwestern University Feinberg School of Medicine, to ABC News.[] “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.”
The CDC notes that the virus can spread in “healthcare settings when not using proper personal protective equipment (PPE) or properly sterilizing equipment.”[]
Clinical implications
Lassa fever causes an Ebola-like illness in some patients.[] Signs and symptoms typically occur 1 to 3 weeks after infection.[] About 80% of infected individuals have mild symptoms—fever, tiredness, weakness, headache—and are not diagnosed. Others experience severe symptoms such as breathing difficulties, bleeding, vomiting, facial edema, pain in the trunk, and shock.
Complications include hearing loss, acute renal failure, and a high risk of miscarriage, according to the CDC.[] Less than 1% of infected patients die, but this increases to 15% for those who become seriously ill and are hospitalized. "Once they get really sick, the death is pretty quick. It's within 7 to 14 days, usually," Dr. Murphy said.[]
Diagnosis and treatment
Patients with a suspected infection—those who may have had contact with an infected person or those who have recently traveled to an area with an active outbreak—should be isolated in a healthcare facility, and HCPs should consult with their local health department.[]
According to the CDC, Lassa fever can be challenging to diagnose because symptoms vary and present similarly to those of other diseases, and testing for the virus is not routine.[][]
Patient’s with Lassa fever can prescribed the antiviral drug ribavirin, along with supportive care, including rest, hydration, and treatment of symptoms.[]
What this means for you
Lassa fever is rare in the US, but it recently claimed one life. If suspected, conduct initial screening to determine exposure risk and signs consistent with the disease. You should coordinate testing decisions with your local health department, aiming for early treatment with ribavirin.