Table 1. Case definition used to detect suspected Lassa fever at Kenema Government Hospital, Kenema, Sierra Leone, October 2006–October 2008*.

Major criteria	Minor criteria
Known exposure to person with suspected Lassa fever	General myalgia or arthralgia
Abnormal bleeding (from mouth, nose, rectum, or vagina)	Headache
Edema of the neck and/or face	Sore throat
Conjunctivitis or subconjunctival hemorrhage	Vomiting
Spontaneous abortion	Abdominal pain/tenderness
Petechial or hemorrhagic rash	Retrosternal pain
Onset of tinnitus or altered hearing	Cough
Persistent hypotension	Diarrhea
Elevated liver transaminases (aspartate aminotransferase higher than alanine aminotransferase)	Profuse weakness Proteinuria Leukopenia (leukocytes <4,000 μL)

*To be tested for suspected Lassa fever, a patient had to have a fever >38°C and not respond to appropriate antimalarial and antimicrobial drug treatment within 72 h.