Lassa fever is an acute viral haemorrhagic illness of 2-21 days duration that occurs in West Africa. The Lassa virus is transmitted to humans via contact with food or household items contaminated with rodent urine or faeces.
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.
Prevention and control
Prevention of Lassa fever relies on promoting good “community hygiene” to discourage rodents from entering homes.
It is important to store grains and other foodstuffs like groceries in rodent-proof containers, disposing of garbage far from the home, maintaining clean households and keeping cats which can chase the rats away.
When buying groceries, remember to clean the packaging of the products where you can, because some of the stores where these products are stored, are rat-infested.
Because Mastomys are so abundant in endemic areas, like Guinea, Nigeria, Liberia and Sierra Leone, 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.
Health-care workers caring for patients with suspected or confirmed Lassa fever should apply extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding.
When in close contact (within 1 metre) of patients with Lassa fever, health-care workers should wear face protection (a face shield or a medical mask and goggles), a clean, non-sterile long-sleeved gown, and gloves (sterile gloves for some procedures).
Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Lassa virus infection should be handled by trained staff and processed in suitably equipped laboratories under maximum biological containment conditions.
On rare occasions, travellers from areas where Lassa fever is endemic export the disease to other countries.
Health-care workers seeing a patient suspected to have Lassa fever should immediately be tested and isolated where necessary, like has been done at the Lagos University Teaching Hospital, LUTH, over the last couple of days.