Lassa fever or Lassa hemorrhagic fever (LHF) is a fever caused by the Lassa virus. It is common in West Africa. One in 80 people who get Lassa fever will die. Some cases are severe and require going to a hospital. These cases have a death rate of 1 in 5. Lassa Fever was discovered in 1969 after two nurses died from the disease. It was named for the town in Borno State, Nigeria where it was first diagnosed.