According to the World Health Organization (WHO), Lassa fever is caused by the Lassa virus. Humans usually contract with the virus through exposure to food or household items contaminated by urine or feces of infected Mastomys rats.
The disease is endemic in the rodent population in parts of West Africa. In some cases, Lassa fever has similar symptoms to malaria, appearing between one and three weeks after exposure to the virus. In mild cases, the disease causes fever, fatigue, weakness, and headache.
The death toll of Lassa fever in Nigeria reached over 170 from nearly 1,000 cases last year till November, amid intensified measures by the government to reduce infections.