ABUJA, March 3 (Xinhua) -- The death toll from Nigeria's Lassa fever outbreak since the beginning of the year had risen to 104, local health authorities said Friday.

In its latest update on the outbreak which has spread to 88 local government areas across 22 states in the country, the Nigeria Center for Disease Control and Prevention (NCDC) said the death toll climbed to 104 as of Feb. 26.

A total of 636 confirmed cases have been so far recorded, the NCDC said, noting with the latest death toll, the case fatality rate had also risen from 16 percent earlier recorded to 16.4 percent.

According to the World Health Organization, Lassa fever is caused by the Lassa virus. Humans usually contract the virus through exposure to food or household items contaminated by the 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.

Last year, the death toll of Lassa fever in Nigeria topped 170 from nearly 1,000 cases amid intensified measures by the government to reduce infections. Enditem