Nigeria: Elevated Lassa fever reported across multiple states through February.

Event

Nigerian authorities have reported more than 1,630 suspected cases of Lassa fever since Jan. 1, including 358 laboratory-confirmed cases, according to data through Feb. 13. This is more than double the roughly 700 cases reported during the same period of 2021. Most cases in 2022 are reported in the states of Ondo, Edo, and Bauchi. Historical data indicates transmission will likely increase and remain high for the coming weeks before tapering downward around weeks 13-15 (early to mid-April). This represents the most updated information as of Feb. 22.

Context

Lassa fever is endemic throughout West Africa, but its prevalence is unknown because nearly 80 percent of human cases are asymptomatic. Nigeria reported 3,498 cases of Lassa fever in 2018, 1,020 cases during December 2016-December 2017, and 921 cases during 2016.

Transmission of Lassa fever typically takes place through human exposure to food or surfaces contaminated by rodent urine or droppings, but it can also be transmitted from person to person through bodily fluids. A person infected with Lassa fever is contagious only when he/she begins displaying symptoms, which include fever, headache, and weakness. However, about 20 percent of infected people develop more serious symptoms such as bleeding (e.g., in the gums, eyes, or nose), difficulty breathing, repeated vomiting, and muscle pain. These symptoms may progress to hearing loss, muscle tremors, and inflammation of the brain.

Advice

Symptoms typically appear one to three weeks after exposure; therefore - if similar symptoms appear - it is important to tell your doctor if you have recently visited Nigeria, where Lassa fever is endemic. Observe basic health precautions and wash hands frequently with soap and water, or use alcohol-based hand sanitizer if soap and water are unavailable. Avoid contact with rodents and their potential habitats near home and work areas, including brush, cluttered firewood, and garbage piles. Keep grain and other foodstuffs in airtight containers. Avoid blood exposure by ensuring that transfusions only take place at facilities that guarantee their safety, and use caution when caring for sick individuals.