A transmission electron micrograph of a number of Lassa virus virions adjacent to some cell debris. The virus, a member of the virus family Arenaviridae, causes Lassa fever.

Abuja — An upsurge of the Lassa fever has left at least 41 people dead in Nigeria since the beginning of the year.

The deaths are out of a total of 258 positive cases at the end of January.

Some 19 states, out of the West African country's 36 states, are enduring outbreaks of the disease spread by rodents.

The states of Ebonyi, Edo and Ondo are the most affected, with 89 percent of confirmed cases.

An outbreak conformed in Maiduguri in the northeast has elicited concern as the town is the epicentre of sporadic outbreaks of cholera.

Maiduguri, the capital city of the state of Borno, is the worst affected by the conflict perpetrated by the Islamist Boko Haram sect.

Thousands in the area are living in inhumane conditions rope for the spread of diseases.

Government has activated the National Emergency Operations Centre in response to the escalating outbreak of Lassa fever.

A treatment centre has been set up in Maiduguri while infection prevention and control training for health care workers is being stepped up.

"While Lassa fever is endemic in Nigeria, the current epidemic trend should be monitored closely and responded to appropriately in order to limit morbidity and mortality," humanitarian agencies responding to the outbreak stated.

Humans usually become infected with the virus through exposure to food or household items contaminated with urine or feces of infected rats.

Lassa fever killed more than 160 people in Nigeria last year.

Some 23 states were affected.