Rare, Ebola-like disease kills one in Iowa: What to know.

An eastern Iowa resident died Monday from a viral disease similar to Ebola that was likely contracted during a recent trip to West Africa.

The person is believed to be the ninth case in the U.S. of Lassa fever in more than half a century, according to the Centers for Disease Control and Prevention. Lassa fever is often transmitted via the waste of an infected rodent found in West Africa. The middle-aged Iowa resident had returned from travel in that region early in October, Iowa public health officials said in a news release.

The CDC is doing final lab testing after the person had a presumptive positive result on Monday. The person died Monday afternoon while hospitalized at the University of Iowa Health Care Medical Center in isolation from other patients. Lassa fever has similar symptoms to the Ebola virus, causing hemorrhagic fever. However, experts say it's far less likely to be fatal than Ebola.

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 typically spreads through the urine or feces of infected rodents. The West African multimammate rat is the only known carrier of the virus. These rats are found in sub-Saharan Africa, and Lassa fever has been found in Sierra Leone, Liberia, Guinea and Nigeria, the CDC said. Humans can spread it through blood or bodily fluids when they have active symptoms. 

In a news release, CDC officials said preliminary information indicates the patient may have had contact with rodents during a visit to West Africa. Officials, who declined to give details on the person, are working to identify others who had contact with the individual around the time the symptoms began.

People in close contact with the infected person will be monitored for three weeks, the CDC said. The incubation period for the virus is between two and 21 days.

Before this case, eight others in the U.S. were identified as having Lassa fever after returning from the region where Lassa fever has been found, the CDC said. About 5,000 people die of the virus each year in West Africa among the approximately 100,000 to 300,000 annual cases, the African Centres for Disease Control and Prevention said. Most people have mild symptoms or no signs of illness at all, and deaths are rare, experts say.

The fatality rate of Lassa fever is much lower than Ebola or Marburg virus, another hemorrhagic fever with a high death rate, said Dr. David Hamer, professor of global health and medicine at Boston University. In the U.S., it’s unlikely that rats would contract Lassa fever or transmit it to humans, he said.

In rural West Africa, rats typically spread the disease when close to human food sources. People can then inhale or come into contact with the virus in rat urine or poop or directly with infected rats.

After someone becomes ill, there is a risk of human spread, especially for family, friends and health care workers who tend to patients with the virus. Infections are also thought to occur through sexual transmission through 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.”

The last Lassa fever case brought to the U.S. was in 2016, according to federal records. Then, a 33-year-old Georgia nurse contracted the illness after she treated an infected patient in Togo. She ultimately recovered. The last death from the virus was in 2015 when a 55-year-old New Jersey man became infected after he worked in Liberia and came in contact with rodents and their waste.

After Monday's death, officials have identified four Americans who have died from Lassa fever, out of nine recorded cases if the illness here.

What are the symptoms of Lassa fever?

The signs and symptoms of Lassa are typically gradual, according to African health officials. Infections are treated with the antiviral drug ribavirin.

Symptoms include fever, weakness and malaise, followed by a headache, sore throat, muscle or chest pain, nausea, vomiting, diarrhea, cough and abdominal pain, according to the African agency that oversees disease control. People with severe cases sometimes experience facial swelling, fluid in the lungs, bleeding from the mouth, nose, genitals or gastrointestinal tract and low blood pressure.

Deafness occurs in 25% of patients who survive the disease, however, most of these patients' hearing returns in the subsequent months. Death usually occurs within two weeks of onset of the disease, the African disease control agency said.

The first documented cases of Lassa fever in the U.S. occurred in 1969. The viral illness takes its name from the Nigerian town where two missionary nurses died from it, according to the U.K. Health Security Agency.

Infections typically occur in the dry season, between December and April, following the reproduction cycle of the multimammate rat in the wet season, the World Health Organization said.