Lassa fever is a severe viral disease occurring mostly in W Africa, characterized by high fever, muscle aches, mouth ulcers, and bleeding in the skin. Lassa fever is an acute viral illness that occurs in West Africa. The illness was discovered in 1969 when two missionary nurses died in Nigeria, West Africa. The cause of the illness was found to be Lassa virus, named after the town in Nigeria (Lassa) where the first cases originated. The causative virus, which is a single-stranded RNA virus, belongs to the virus family called arenaviruses and is harbored by a rat, Mastomys natalensis.
Mode of transmission
The reservoir, or host, of Lassa virus is a rodent known as the “multimammate rat” of the genus Mastomys. There are a number of ways in which the virus may be transmitted, or spread, to humans. The Mastomys rodents shed the virus in urine and droppings. Therefore, the virus can be transmitted through:
1. Direct contact with these materials, through touching objects or eating food contaminated with these materials, or through cuts or sores.
2. Person-to-person infections and laboratory transmission can also occur, particularly in hospitals lacking adequate infection prevent and control measures. That is why the disease can also be caught by medical personnel treating patients in hospitals.
3. Contact with the virus also may occur when a person inhales tiny particles in the air contaminated with rodent excretions. This is called aerosol or airborne transmission.
4. Because Mastomys rodents are sometimes consumed as a food source, infection may occur via direct contact when they are caught and prepared for food.
Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes into contact with the virus. Following fever and general malaise, later stages of the disease may include abdominal pain, diarrhea, vomiting, conjunctivitis, facial swelling, proteinuria (protein in the urine), mucosal bleeding and petechiae (pinpoint, round spots that appear on the skin as a result of bleeding), tiny purplish spots in the skin caused by leakage of blood from the capillaries. Hearing loss, tremors and encephalitis (inflammation of the brain, caused by infection or an allergic reaction). Heart and kidney failure may also occur in severe cases, and mortality is high, ranging from about 15% to, among pregnant women, as much as 60%.
Primary transmission of the Lassa virus from its host to humans can be prevented by avoiding contact with Mastomys rodents, especially in the geographic regions where outbreaks occur. Putting food away in rodent-proof containers and keeping the home clean help to discourage rodents from entering homes. Using these rodents as a food source is not recommended. Trapping in and around homes can help reduce rodent populations.
When caring for patients with Lassa fever, further transmission of the disease through person-to-person contact or nosocomial routes can be avoided by taking preventive precautions against contact with patient secretions (together called VHF isolation precautions or barrier nursing methods). Such precautions include wearing protective clothing, such as masks, gloves, gowns, and goggles; using infection control measures, such as complete equipment sterilization; and isolating infected patients from contact with unprotected persons until the disease has run its course.
Ribavirin, an antiviral drug, has been used with success in Lassa fever patients. It has been shown to be most effective when given early in the course of the illness. Patients should also receive supportive care consisting of maintenance of appropriate fluid and electrolyte balance, oxygenation and blood pressure, as well as treatment of any other complicating infections.
The federal government has warned that the current outbreak of Lassa fever could kill 1,000 Nigerians, adding that it has spread to 17 states in the country, with Edo, Rivers, Nasarawa and Taraba States identified as hotspots of the virus. The three states identified as hotspots joined Bauchi, Kano and Niger States, which have recorded a high incidence of the disease.
The Minister of Health, Prof. Isaac Adewole maintained that so far the Lassa fever virus had spread to 64 local governments areas in 17 states, with the country recording 212 suspected cases
By Pharm. Okafor S.N.