Fox News reported April 7 that a case of Lassa fever has been diagnosed in a traveler from West Africa. The patient was admitted to a Minnesota hospital on March 31. The illness is endemic to West Africa but is rarely seen in the U.S., with the last case appearing four years ago.
The Centers for Disease Control issued a press release about a patient with Lassa fever on April 4. The risk to other travelers is considered "extremely low."
“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,” said CDC Director Tom Frieden, M.D., M.P.H.
Lassa fever was first discovered in 1969, after the deaths of two nurses in Lassa, Nigeria, the CDC states. The illness is carried by a rodent called the multimammate rat, Mastomys natalensis. The viral infection is spread to humans in one of several ways.
- consumption of food or drink contaminated with rodent urine or feces
- inhalation of airborne particles of dried feces
- touching contaminated surfaces or getting rodent excreta in open cuts or sores
- reuse of dirty needles in a healthcare setting
- extremely close contact with an infected patient in a healthcare setting without using personal protective equipment
The illness is not believed to be transmitted through casual personal contact. Even skin to skin contact is considered safe if no bodily fluids are present.
Symptoms of Lassa fever vary. As many as 80 percent of patients are never diagnosed due to the mildness of their symptoms. Severe illnesses may involve hemorrhaging, trouble breathing, shock, neurological problems or death. The CDC estimates that up to 33 percent of patients suffer some degree of deafness from their illness and the complication is not related to the severity of the illness. Women in the third trimester of pregnancy have a very high death rate, and spontaneous abortion is another serious complication of a Lassa fever infection.
Like all viral illnesses, there is no cure for Lassa fever. Medical treatment consists of supporting the patient, through fluids, oxygen and other interventions. Where available, the anti-viral medication Ribavirin has been used with success in the early stages of the disease.
At this time, the risk of catching Lassa fever appears confined to the West African habitat of its rodent vector. No other rodent is known to carry the virus. As Dr. Frieden noted, the single case of Lassa fever in Minnesota is just a demonstration of how little travel time is needed for an illness to move thousands of miles.