Rare West African virus confirmed in Minnesota traveler, search on for others exposed

This hematoxylin-eosin-stained (H&E) photomicrograph depicts the cytoarchitectural changes found in a liver tissue specimen extracted from a Lassa fever patient. (CDC.gov)

A traveler who flew back to the United States from West Africa was diagnosed with the rare and sometimes deadly Lassa fever, said health authorities who on Friday were trying to identify others on the plane who may have been exposed.

In the first Lassa case in the United States in four years, an unnamed patient was admitted to a Minnesota hospital on Monday suffering from fever and confusion, the U.S. Centers for Disease Control and Prevention said in a statement.

Blood samples sent to CDC tested positive for Lassa fever on Thursday.

The patient was recovering and in stable condition on Friday, the CDC said.

While the likelihood of human-to-human transmission of the virus is "considered extremely low," the CDC was reaching out to airlines to identify passengers and crew who had close contact with the infected individual. Once found, the people will be notified by state and local health departments.

"People will not get this infection just because they were on the same airplane or in the same airport," said CDC epidemiologist Barbara Knust in the statement. "Casual contact is not a risk factor for getting Lassa fever."

Lassa fever is a severe viral disease common in West Africa but rarely seen in the United States.

In West Africa, as many as 300,000 cases of Lassa fever are reported every year, with about 5,000 ending in death, the CDC said. The virus is carried by rodents and transmitted to humans through contact with urine or feces.

The last U.S. case was reported in Pennsylvania in 2010, the statement said. Previously, seven other cases, all travel related, were identified in the United States.

"This imported case is a reminder that we are all connected by international travel. A disease anywhere can appear anywhere else in the world within hours," CDC Director Tom Frieden said in a statement.

While Lassa fever can cause hemorrhagic symptoms in infected individuals, it is not related to the Ebola virus, which recently resurged in West Africa, the CDC said.