A person from Iowa who recently returned to the United States from West Africa has died after contracting Lassa fever, a virus that can cause Ebola-like illness in some patients. State health officials reported the case on Monday.
“I want to assure Iowans that the risk of transmission is incredibly low in our state. We continue to investigate and monitor this situation and are implementing the necessary public health protocols,” Robert Kruse, state medical director of the Iowa Department of Health and Human Services, said in a statement posted to the department’s website.
The unnamed person was described as a middle-aged individual from eastern Iowa. The statement said the person had been cared for at University of Iowa Health Care. It did not indicate how long he or she had been in care or if the individual had sought care anywhere else before being admitted to the hospital.
That is important because while person-to-person spread of the Lassa virus is rare, transmission can occur in health care settings, especially if health workers don’t realize they are dealing with a patient who has the disease and don’t take adequate precautions. Testing conducted on Monday by the Nebraska Laboratory Response Network indicated the person had Lassa fever; confirmatory testing will be done by the Centers for Disease Control and Prevention.
No details were released about when the person developed symptoms or even when he or she returned to the United States. The CDC said in a statement, however, that the individual was not sick while traveling, so “the risk to fellow airline passengers is extremely low.”
Although there have been previous Lassa fever cases imported to the United States, they are not common occurrences. The statement said there have been eight known imported cases, including the new one, in the past 55 years.
There was a case in May 2015, in a New Jersey resident who had traveled to Liberia and another in a New Jersey resident in 2004. Both those people died. Minnesota reported a case in 2014; that person recovered.
Lassa fever is endemic to a number of countries in West Africa, including Nigeria, Ghana, Guinea, Sierra Leone, and Liberia. In these countries, the virus causes several hundred thousand infections and about 5,000 deaths every year.
The main source of the virus is a rodent called the multimammate rat. People contract the virus either by handling or eating infected rodents, or as a result of having the rodents in their homes. Food or household items that have been contaminated with urine or feces from infected rodents can transmit the disease.
Though severe Lassa fever causes symptoms like those seen with Ebola infection, it does not trigger large chains of human cases, as can occur during Ebola outbreaks, said Armand Sprecher, a viral hemorrhagic fever expert who works for Doctors Without Borders.
“You don’t see a lot of human-to-human transmission,” Sprecher told STAT. “Most people get it from the source, the reservoir.”
The World Health Organization says that about eight of 10 people who contract the virus have no or only mild symptoms, which include headache, fatigue, and low-grade fever.
In those that go on to develop severe illness, symptoms can include bleeding, difficulty breathing, vomiting, and shock, according to the CDC. The WHO suggests that about 15% of people who develop severe Lassa disease die from the condition.
The death rate can be much higher in some places, said Robert Garry, a professor at Tulane Medical School in New Orleans who has been studying Lassa fever for the past couple of decades. In Sierra Leone, where Garry has research projects, the fatality rate among severe cases can be as high as 70%, he said. Good supportive care — for instance replenishment of fluids — can increase the chances of survival, he said.
He agreed that most cases are people who are infected by an animal source, but said some person-to-person transmission can occur, especially in hospitals. “It happens in West Africa, even in places where they’re very aware of the possibility [of Lassa cases]. So, yeah, if you were not expecting a disease like that to show up in your hospital, it could happen.”
That said, Garry said he doesn’t expect to see transmission here. “There’s very little chance that this is going to spread beyond that hospital setting. But they have to do the case contacts [investigations] and all that to make sure.”
Of the diseases that cause viral hemorrhagic fevers — things like Ebola and Marburg fever — Lassa is probably the one that is most commonly imported to non-endemic countries, Garry said.