Since November 2015, Nigeria, Benin, Sierra Leone and Togo have reported more than 300 cases of Lassa fever and 164 deaths. Nigeria accounts for the majority of the cases with 266 cases and 138 deaths reported in 22 of the country’s 34 provinces. Benin has recorded 51 cases and 25 deaths, Togo and Sierra Leone each reported two cases.
Lassa virus is carried by the Mastomys rat, which is found in parts of West Africa. The virus is transmitted to humans from direct contact with infected rats by catching and preparing them for food, or through contact with food or household items contaminated with rat feces or urine. The virus can also be transmitted through contact with an infected person’s body fluids.
Around 80 percent of people who become infected with Lassa virus have no symptoms or they have symptoms that mimic other illnesses, such as malaria, making it difficult to treat them. Symptoms include fever, fatigue, nausea, vomiting, diarrhea, headaches, abdominal pains, sore throat and facial swelling.
“Without early diagnosis and treatment, 1 in 5 infections result in severe disease, where the virus affects several organs such as the liver, spleen and kidneys,” explains Dr. Pierre Formenty, an expert in hemorrhagic fevers at the World Health Organization (WHO). “We need resources to invest in diagnostics to easily, accurately and safely test for Lassa fever as we do for malaria and HIV. Without a proper diagnosis, many people do not receive the correct treatment and that is why we see so many people with Lassa fever dying each year.”
Ribavirin has been used successfully in the treatment of confirmed Lassa cases. This drug can treat infected people if it is administered as soon as the first signs appear.
The first known case of Lassa infection outside of Africa has been reported in Germany. One person, a funeral home employee was infected after direct contact with an American who died of the disease in February 2016. The American was a medical director of a missionary hospital in Togo who was evacuated to Germany where he died.
“This is the first time that secondary transmission of the infection is reported in Europe,” says Formenty. “The risk for further transmission of Lassa fever in Germany and also West Africa is low and limited to hospital settings caring for the cases, with all contacts accounted for and monitored.”
WHO continues to monitor the epidemiological situation and conduct risk assessments based on the latest available information.