About 80 per cent of people infected with the Lassa virus have no symptoms, the World Health Organisation has said.
The WHO also revealed that 1 in 5 infections result in severe disease, where the virus affects several organs such as the liver, spleen and
kidneys.
Lassa fever is a zoonotic disease, meaning that humans become infected from contact with infected animals.
The animal reservoir or host of Lassa virus is a rodent of the genus Mastomys, commonly known as the “multimammate rat.” Mastomys rats infected with Lassa virus do not become ill, but they can shed the virus in their urine and faeces.
“Because the clinical course of the disease is so variable, detection of the disease in affected patients has been difficult,” WHO stated.
When the presence of the disease is confirmed in a community, however, prompt isolation of affected patients, good infection prevention and control practices, and rigorous contact tracing can stop outbreaks.
Key facts
Lassa fever is an acute viral haemorrhagic illness of 2 to 21 days duration that occurs in West Africa.
The Lassa virus is transmitted to humans via contact with food or household items contaminated with rodent’s urine or faeces.
Person-to-person infections and laboratory transmission can also occur, particularly in hospitals lacking adequate infection prevention and control measures.
Lassa fever is known to be endemic in Benin, Ghana, Guinea, Liberia, Mali, Sierra Leone, and Nigeria, but probably exists in other West African countries as well.
Early supportive care with rehydration and symptomatic treatment improves survival.
Symptoms of Lassa fever
The incubation period of Lassa fever ranges from 6 to 21 days. The onset of the disease, when it is symptomatic, is usually gradual, starting with fever, general weakness, and malaise. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. In severe cases, facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop.
Lassa fever occurs in all age groups and both sexes. Persons at greatest risk are those living in rural areas where Mastomys are usually found, especially in communities with poor sanitation or crowded living conditions. Health workers are at risk if caring for Lassa fever patients in the absence of proper barrier nursing and infection prevention and control practices.
Prevention
Prevention of Lassa fever relies on promoting good “community hygiene” to discourage rodents from entering homes. Effective measures include storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, maintaining clean households and keeping cats.
The world health body further advised, “Because Mastomys are so abundant in endemic areas, it is not possible to completely eliminate them from the environment. Family members should always be careful to avoid contact with blood and body fluids while caring for sick
persons.
“In health-care settings, staff should always apply standard infection prevention and control precautions when caring for patients, regardless of their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal protective equipment (to block splashes or other contact with infected materials), safe injection practices and safe burial practices.”
