Lassa Fever Explained: Insights After the Death of an Iowa Resident

The person had returned recently from a trip to West Africa. Lassa fever is a viral disease similar to the Ebola virus.

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A resident of eastern Iowa passed away on Monday from a virus similar to Ebola, likely contracted during a recent visit to West Africa. According to the CDC, this is believed to be the ninth case of Lassa fever in the U.S. in over 50 years.
The disease, which is often spread through contact with waste from infected rodents in West Africa, was diagnosed in the middle-aged Iowa resident who had returned from the region in early October, Iowa public health officials reported in a news release.
The CDC is conducting final lab tests after the individual received a preliminary positive result on Monday.
The person passed away that afternoon while in isolation at the University of Iowa Health Care Medical Center. Lassa fever, which shares symptoms with Ebola and causes hemorrhagic fever, is considered much less deadly, according to experts.
State and federal officials have said the risk of transmission is low. The person didn’t become sick while traveling, so the risk of the disease spreading to fellow passengers is “extremely low,” the CDC said.
“We continue to investigate and monitor this situation and are implementing the necessary public health protocols,” Dr. Robert Kruse, state medical director at the Iowa Department of Health and Human Services, said in a statement.
Lassa fever usually spreads through the urine or feces of infected rodents, with the West African multimammate rat being the only known carrier of the virus.
These rats inhabit sub-Saharan Africa, and Lassa fever cases have been reported in Sierra Leone, Liberia, Guinea, and Nigeria, according to the CDC. The virus can also be transmitted between humans through blood or bodily fluids when symptoms are present.
In a news release, CDC officials stated that initial information suggests the patient may have come into contact with rodents during their trip to West Africa. While officials did not provide specific details about the individual, they are actively working to identify others who may have had contact with the patient around the time symptoms started.
The CDC reported that individuals who were in close contact with the infected person will be monitored for three weeks, as the incubation period for the virus ranges from two to 21 days. Prior to this case, there were eight other instances of Lassa fever identified in the U.S. among individuals returning from regions where the virus is present.
According to the African Centres for Disease Control and Prevention, approximately 5,000 people die from Lassa fever each year in West Africa out of an estimated 100,000 to 300,000 annual cases. Most individuals experience mild symptoms or none at all, and fatalities are considered rare, according to experts.
Dr. David Hamer, a professor of global health and medicine at Boston University, noted that the fatality rate of Lassa fever is significantly lower than that of Ebola or Marburg virus, both of which are hemorrhagic fevers with high mortality rates. He added that in the U.S., it is unlikely for rats to contract Lassa fever or pass it on to humans.
In rural West Africa, the disease is typically spread by rats that come into proximity with human food sources, allowing people to inhale or come into contact with the virus through rat urine or feces, or directly from infected rats.
Once an individual becomes ill, there is a risk of human-to-human transmission, particularly among family members, friends, and healthcare workers caring for the infected person. Additionally, the virus is believed to spread through sexual transmission via the exchange of bodily fluids.
Human transmission, Hamer said, “makes it a worry for potential introduction and spread in the United States.” However, he noted, “This is the ninth case since the sixties. So it’s been a rare event.”
According to federal records, the most recent case of Lassa fever reported in the U.S. occurred in 2016 when a 33-year-old nurse from Georgia contracted the virus after treating an infected patient in Togo; she eventually recovered.
The last reported death from Lassa fever was in 2015, when a 55-year-old man from New Jersey became infected after working in Liberia and coming into contact with rodents and their waste. Following the death on Monday, officials noted that four Americans have died from Lassa fever out of nine recorded cases in the U.S.
Symptoms of Lassa Fever
According to health officials in Africa, the signs and symptoms of Lassa fever usually develop gradually. Infections are treated with the antiviral medication ribavirin.
Initial symptoms include fever, weakness, and general discomfort, which can progress to headaches, sore throat, muscle or chest pain, nausea, vomiting, diarrhea, cough, and abdominal pain, as reported by the African agency responsible for disease control. In more severe cases, individuals may experience facial swelling, fluid accumulation in the lungs, bleeding from the mouth, nose, genitals, or gastrointestinal tract, and low blood pressure.
According to the African disease control agency, about 25% of patients who survive Lassa fever experience deafness, though most see their hearing return in the following months. Death typically occurs within two weeks of the onset of symptoms.
The first recorded cases of Lassa fever in the U.S. were identified in 1969. The disease is named after the Nigerian town where two missionary nurses lost their lives to it, as noted by the U.K. Health Security Agency.
According to the World Health Organization, infections usually happen during the dry season, from December to April, as this follows the reproductive cycle of the multimammate rat, which occurs during the wet season.
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