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
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