Most individuals (80%) who are infected with the Lassa virus do not have any symptoms or only mild symptoms.
Symptoms of Lassa fever begin 1-3 weeks after infection. Mild symptoms of Lassa fever may include low fever, headache, sore throat, cough, weakness, muscle pain, and malaise.
Symptoms of more severe cases of Lassa fever may include facial swelling; hair loss; gait disorder; hearing loss; encephalitis (brain inflammation); nausea and vomiting; diarrhea; fluid in the lungs; respiratory distress; tremors; chest, back, or abdominal pain; miscarriage; hemorrhaging in the eyes, nose, gums, or gastrointestinal tract; low blood pressure; shock; seizures; coma; multi-organ failure; and death.
The most common complication of Lassa fever is either temporary or permanent deafness.