Officials with Emory University Hospital in Atlanta report expecting a patient from West Africa with suspected Lassa fever this weekend.

Image/ C. S. Goldsmith, P. Rollin, M. Bowen This transmission electron micrograph (TEM) depicted numbers of Lassa virus virions adjacent to some cell debris.  The virus, a member of the virus family Arenaviridae, is a single-stranded RNA virus, and is zoonotic, or animal-borne that can be transmitted to humans. The illness, which occurs in West Africa, was discovered in 1969 when two missionary nurses died in Nigeria, West Africa.In areas of Africa where the disease is endemic (that is, constantly present), Lassa fever is a significant cause of morbidity and mortality. While Lassa fever is mild or has no observable symptoms in about 80% of people infected with the virus, the remaining 20% have a severe multisystem disease. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50%. There are a number of ways in which the virus may be transmitted, or spread, to humans. The Mastomys rodents shed the virus in urine and droppings. Therefore, the virus can be transmitted through direct contact with these materials, through touching objects or eating food contaminated with these materials, or through cuts or sores. Because Mastomys rodents often live in and around homes and scavenge on human food remains or poorly stored food, transmission of this sort is common. Contact with the virus also may occur when a person inhales tiny particles in the air contaminated with rodent excretions. This is called aerosol or airborne transmission. Finally, because Mastomys rodents are sometimes consumed as a food source, infection may occur via direct contact when they are caught and prepared for food.
C. S. Goldsmith, P. Rollin, M. Bowen

The patient’s diagnosis is not yet confirmed. Emory will work closely with the Centers for Disease Control and Prevention (CDC) and with the Georgia Department of Public Health in diagnosing the patient.

The patient, who due to confidentiality regulations cannot be identified, is an American physician assistant working for a missionary organization in Togo, West Africa. Emory was contacted by the U.S. State Department and asked to accept the patient in its Serious Communicable Diseases Unit (SCDU) , an isolation unit within the hospital in which four patients with Ebola virus disease were successfully treated in 2014.

Lassa is an acute viral infection that has been prevalent in West Africa. Lassa fever is different from Ebola. Although Lassa fever and Ebola can result in similar symptoms, Lassa fever is less likely than Ebola to spread from person to person and is far less deadly. The death rate from Lassa fever is approximately 10 to 20 percent in hospitalized patients, versus approximately 70 percent in Ebola virus disease patients. While both diseases are viral hemorrhagic fevers, bleeding and severe symptoms are not common in cases of Lassa fever.

Lassa fever has been endemic in Africa for many years, with an estimated 100,000 to 300,000 people being infected each year.

It is primarily spread through direct contact with or the inhalation of droppings from “multimammate” rodents that carry the virus.

The virus can be transmitted by infected humans, but only through direct contact with bodily fluids. It cannot be transmitted through casual contact, and is not an airborne virus.

According to the CDC there have been only a few cases of Lassa fever reported in the United States, the most recent being in one patient in 2015 and one patient in 2010.