The Centers for Disease Control and Prevention (CDC) and the Minnesota Department of Health (MDH) have confirmed a diagnosis of Lassa fever in a person returning to the United States from West Africa. The patient was admitted to a hospital in Minnesota on March 31 with symptoms of fever and confusion. Blood samples submitted to CDC tested positive for Lassa fever on April 3. The patient is recovering and is in stable condition.
“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,” says CDC director Tom Frieden, MD, MPH.
Lassa fever is a severe viral disease that is common in West Africa but rarely seen in the United States. Seven other Lassa fever cases, all travel related, have been identified in the United States, with the last one reported in Pennsylvania in 2010. Although Lassa fever can produce hemorrhagic symptoms in infected persons, the disease is not related to Ebola hemorrhagic fever, which is responsible for the current outbreak in West Africa.
In West Africa, Lassa virus is carried by rodents and transmitted to humans through contact with urine or droppings of infected rodents. In rare cases it can be transmitted from person to person through direct contact with a sick person’s blood or bodily fluids, through mucous membrane, or through sexual contact. The virus is not transmitted through casual contact. About 100,000 to 300,000 cases of Lassa fever, and 5,000 deaths related to Lassa fever, occur in West Africa each year.
CDC is working with public health officials and airlines to determine the patient’s travel route from West Africa and identify any passengers or others who may have had close contact with the infected person. Preliminary information indicates that the patient flew from West Africa to New York City and caught another flight to Minneapolis.
“Given what we know about how Lassa virus is spread to people, the risk to other travelers and members of the public is extremely low,” says Martin Cetron, MD, MPH, director of CDC’s Division of Global Migration and Quarantine.
“Casual contact is not a risk factor for getting Lassa fever,” says Barbara Knust, DVM, MPH, an epidemiologist in CDC’s Division of High-Consequence Pathogens and Pathology, which performed the laboratory testing. “People will not get this infection just because they were on the same airplane or in the same airport.”
As part of its investigation, CDC is working with the airlines to gather contact information for passengers and crew who were seated near the infected individual. CDC will provide passenger contact information to state and local health departments where the passengers live to notify them about their possible exposure.
For additional information about Lassa fever see the CDC website at http://www.cdc.gov/vhf/lassa/.
For more information about airline contact investigations see http://www.cdc.gov/quarantine/contact-investigation.html.