What is Lassa Fever?
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. The cause of illness was found to be Lassa virus-names after the town in Nigeria where the first cases originated. The virus, a member of the virus family Arenaviridiae, is a single-stranded RNA virus, zoonotic or animal borne.
In areas of Africa where the disease is endemic (that is constantly present), lassa fever is a significant cause of morbidly and mortality.
While lassa fever is mild or has no observable symptoms in about 80.0% by people infected with the virus, the remaining 20.0% have a severe multi-systemic disease. Lassa fever is also associated with occasional epidemics, during which the case fatality rate can reach 50.0%.
Where is Lassa Fever Found?
Lassa fever is an endemic disease in parts of West Africa. It is recognized in Guinea, Liberia, Sierra-Leone as well as Nigeria. However, because the rodent species which carry the virus is found throughout West Africa, the actual geographic range of the disease may extend to other countries in the region.
How Many People Become Infected?
The number of lassa virus infections per year in West Africa is estimated at 100,000 to 300,000 with approximately 5,000 deaths.
Unfortunately, such estimates are crude because surveillance for cases of the disease is not uniformly performed. In some areas of Sierra Leone and Liberia, it is know that 10% – 16% of people admitted in hospital have lassa fever which indicates the serious impact of the disease on the population of this region.
In What Animal Host is Lassa Virus Maintained?
The reservoir, or host of Lassa virus is a rodent known as mastomys rodent, also known as the “Multimammate rat”. “Note the hairless tail”, “multimammate rat” of the genius mastomys. It is not certain which species of mastomys are associated with Lassa. However, at least two species carry the virus in Sierra-Leone. Mastomys rodent breed very frequently, produce large numbers of offsprings, and are numerous in the Savannah and Forests of West Central, and East Africa. In addition, mastomys generally readily colonize human homes. All these factors together contribute to the relatively efficient spread of Lassa Virus from infected rodents to humans.
How Do Humans Get Lassa Fever?
There are a number of ways in which the virus may be transmitted, or spread to humans. The mastomys rodent shed the virus in urine and droppings. Therefore the virus can be transmitted through direct contact with these materials, through touching the objects used for food or cooking utensils or by eating food contaminated with urine or droppings of the mastomys rat or through cuts or sores contaminated with the droopings of the rat. Mastomys rats often live in and around homes and scavenge on human food remains especially in villages where food substances are spread on the floor. Such food as garri when can be contaminated when spread on the floor and infection may occur when an individual takes such soaked garri. Transmission may occur when a person inhales tiny particles in the air contaminated with rodent excretions.
Finally, because mastomys rodents are sometimes consumed as a food source, infection may occurs via direct contact when they are caught and prepared for food.

Lassa fever may also spread through person-to person contact. This type of transmission occurs when a person comes in contact with virus in blood, tissue, secretions or excretions of an infected individual. The virus cannot spread through casual contact like skin to skin contact without exchange of body fluids. Person to person transmission is common in both village and health care settings where along with the above-mentioned modern of transmission, the virus may also be spread in contaminated hospital equipment like needles (nosocomial transmission).
What are the Signs and Symptoms of Lassa Fever?
Signs and symptoms of Lassa fever typically occur 1-3 weeks after the patient comes in contact with the virus. These include fever, hypertension, diarrhea, proteinuria (excess protein in urine), mucosal bleeding (bleeding from gums), neurological problems like hearing loss, retrosternal pain (pain behind the chest wall), sore throat, back pain, cough, abdominal pain, vomiting, general malaise, anorexia or loss of apetite, night mares, rigor.
Because the symptoms of Lassa fever are so varied and non specific, clinical diagnosis is usually difficult. There should be high index of suspicious of the disease in an individual who presents with the above symptoms in an area where lassa fever is very common.
How is Lassa Fever Treated
A comprehensive and specialized test is carried out using the patient’s blood sample.
Ribavirin, an antiviral drug has been used with success in Lassa fever patients. It has been shown to be most effective when given in the early course of illness.
Patients should also receive supportive care, correction and maintenance of appropriate fluid and electrolyte balance, oxygenation, as well as treatment of any other complicating infections.
Prevention / Control of Lassa Fever
Prevention of Lassa fever is better than attempt at curing the disease considering the disease fatality rate.
Primary transmission of Lassa virus from its host to humans can be prevented by avoiding contact with mastomy rodents (rats), especially in the geographic regions where outbreak of lassa fever occurs.
Putting food away in rodent proof containers and keeping the home clean help to discourage rodents from entering homes.
Using these species of rodents as food source is not recommended.
Trapping in and around homes can help reduce rodent populations.
Spreading of food substances on the floor as is the practice in some villages should be discouraged.
When caring for patients with Lassa fever, further transmission of the disease through person to person should be minimized by barrier and reverse barrier nursing. Such precautions or barrier nursing methods include wearing of protective clothing such as masks, gloss, gown and goggles. Contact or nosocomial routes can be avoided by taking preventive precautions against contact with secretion.
Isolation of infected patients until disease has run its course.
Further educating people in high risk areas about ways to decrease rodent populations in their home will acid in the control and prevention of Lassa fever. Other challenges include developing more rapid diagnostic tests and increasing the availability of the only known drug treatment. Research is presently underway in develop a vaccine for Lassa fever.
In addition, government should designate more centres across the country for the treatment of Lassa fever.

MRS TESSY EYAKWANOR
Chief Nursing Officer, Institute of Child Health, University of Benin, Benin City
Edo State, Nigeria
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