WHAT IS LASSA FEVER?
Lassa fever is a severe and often fatal Hemorrhagic illness caused by Lassa Virus. It was first discovered in 1969 in the village of Lassa in Borno State, Nigeria since then; there have been countless outbreaks across West-Africa.
Lassa Virus is a member of the Arenaviradae Virus family. Human contract the virus primarily through contact with the contaminated excreta of Mastomys natalensis rodents commonly known as the Multimammate rat which is natural reservoirs for the virus, Arena virus are stable and infectious by the aerosol route in non-human primates. The rodents live in houses with humans and deposit excreta on floors, tables, beds and food.
Estimates of annual incidence of Lassa fever across this region reach as high as 300,000 infections and 5000 deaths. This disease is known to be endemic in Nigeria, Sierra Leone, Liberia, Guinea and the Central Africa Republic; there is also an evidence of infection in nearby countries including Mali, Senegal, and Democratic Republic of Congo.
HOW DO ONE GET INFECTED.
Lassa is Zoonotic which means transmission can occur from animals to humans by Mastomys natalensis. They are predominantly found in rural areas. The virus is shed in their excreta (urine and feaces) which can be aerolized and inhaled by humans.
Infection in humans occurs via exposure to animal excrement through the respiratory or gastrointestinal tracts ;through broken skin or mucous membranes that are directly exposed to infective materials .Region where Lassa is endemic, rats are consumed as food, which in turn lead to infection.
Transmission from person to person has been established, it can be contracted by an airborne route or with direct contact with infected human blood, urine, semen or vaginal fluids.
Between individuals caring for sick patients are infected, although anyone who comes into close contact with a person carrying the virus is at risk of infection.
In early stages, Lassa fever is often misdiagnosed as influenza, typhoid or malaria. The onset of the illness is typically indolent, with no specific symptoms that would distinguish it from other febrile illnesses.
Early symptoms include: fever, headache, general malaise, following by sore throat, nausea, vomiting, abdominal pain and diarrhea in some cases. Common symptoms with cases of Lassa fever include fever, sore throat, headache, red eyes, weakness, facial edema, restrosternal pain (behind the chest wall) , generalized abdominal pain, epistaxis and haemoptysis. Other features include low blood pressure, raised pulses rate, nasal flaring and bibasal crepitations. In severe cases bleeding from mucosal membranes such as the mouth can also be observed. The virus excreted in urine for 3-9weeks and semen for 3 months.
After 4-7 days, many patients’ starts to feel better, but a small minority will proceed to display symptoms such as edema, hypertension, bleeding and shock. Death from Lassa fever is most commonly occurs 10-14days after symptom onset.
HOW YOU AVOID BEING INFECTED
v Health care workers should take precautions by wearing protective clothing, such as masks, gloves, gowns and goggle.
v Isolate infected patients or their blood samples from contact with unprotected persons.
v Putting food away on rodent proof containers.
v Keeping the home clean to discourage rodents from entering
v Trapping in and around homes can help reduce rodent population.
v Using these rodents as a food source is not recommended.
There is no vaccine for Lassa fever presently, the only drug available is RIBAVIRIN which is only effective if administered early.
Severe cases of Lassa fever are usually associated with multi organ complications with significantly raised levels of liver enzymes such as AST (Aspartate aminotranferase) and ALT ( Alanine amino tranferase). The serum from these patients can turn brownish in colour and a significant degree of haemolysis can be observed.
The antibody response is generally slow in infected patients and the presence of this can be detected by enzyme-linked immunosorbent assay (ELISA) Indirect Fluorescent antibody techniques.
Leukocyte counts may be low, normal or moderately elevated,
Platelet counts are usually normal but might be slightly low,
Excessive amount of albumin proteins in the urine,
ECGs are usually abnormal.