Lassa fever is an acute viral disease caused by the Lassa virus, which is a member of the Arenaviridae family. It is endemic in West Africa and is spread through contact with infected rodents. Symptoms of the disease include fever, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, and facial swelling. In severe cases, it can cause bleeding from the mouth, nose, and eyes, as well as neurological problems. Treatment includes supportive care and antiviral medications.