LASSA FEVER

LASSA FEVER

Lassa fever is an acute viral hemorrhagic fever caused by the Lassa fever, a member of the Arenaviridae family. It is an enveloped single-stranded bisegmented RNA virus. It was first discovered in 1969 in the town of Lassa, in Borno State, Nigeria, in the red scram river valley at the south end of Lake Chad. However, it can be found in other places, especially in West Africa e.g. Liberia, Guinea, Sierra Leone, and the Central African Republic, but it is believed that human infections also exist in Democratic Republic of the Congo, Mali and Senegal.

The primary animal host of the Lassa virus is the Natal Multi-mammate Mouse (Mastomy, nat6alensis), an animal indigenous to most of sub-haran Africa.

Lassa virus is zoonotic (transmitted from animals), in that it spreads to man from rodents, specifically multi-mammate rats. This is probably the most common rodent in equatorial Africa, ubiquitous in human households and eaten as a delicacy in some areas. In these rats infection is in a persistent asymptomatic state. The virus is shed in their excreta (urine and faeces), and people become infected by eating food contaminated with the rat excreta. Infections in human occurs by direct contact or inhalation of infected body fluids such as urine, blood, saliva etc. It is also possible to acquire the infection through broken skin or mucous membranes that are directly exposed to infective material. Transmission from person to person has also been established, presenting a disease risk for those living in areas of poor sanitation and health workers managing such cases. Sexual transmission has not been reported.

Some cases have severe multi-system disease, where the virus affects several organs in the body, such as the liver, spleen, and kidneys. The incubation period of Lassa fever ranges from 6 – 21 days. The onset of the disease is usually gradual, starting with fever, general weakness and malaise. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhea, cough, and abdominal may follow. Severe cases may progress to show facial swelling, fluid in the lung cavity, bleeding from mouth, nose, vagina or gastrointestinal tract and low blood pressure. Protein may be noted in the urine. Shock, seizures, tremor, disorientation, and coma may be seen in the late stages. Deafness occurs in 25% of patients of whom half recover, some function after 1-3 months. Transient hair loss and gait disturbance may occur during recovery. In some cases of Lassa fever; it usually lead to death. Death usually occurs within 14days of onset in fatal cases.

Prevention of Lassa fever centers 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. These should be done because Mastomys are so abundant in endemic areas, it is not possible to completely eliminate them from the environment. Family members and health care workers should always be careful to avoid contact with blood and body fluids while caring for sick persons. Patients suspected to have Lassa fever should be cared for under specific isolation precautions’, which include the wearing of protective clothing such as masks, gloves, gowns, and face shields, and the systematic sterilization of contaminated equipments to avoid infection.

To prevent Lassa fever, contacts between rats and human being should be avoided. The house and environment should be kept clean always. The environment should be fumigated periodically. All food & water should be covered thoroughly and household utensils should be kept clean. All holes and rats hideouts should be blocked.

Nigeria is once again experiencing an upsurge in reported cases of the deadly Lassa fever. The latest outbreak, which has claimed no fever than 40 lives, has affected three hundred and ninety-seven (397) across 12 states of the federation. Of the reported cases, only eighty-seven (87) have been confirmed clinically, according to the minister of health, Onyebuchi Chukwu studies conducted by the global health body, the World Health Organization (WHO) show that between 300,000 and 500,000 cases of Lassa fever occur annually, from which 5000 deaths are recorded in the endemic West African States of Sierra Leone, Guinea, Libera and parts of Nigeria. Although first recognized in 1969 at the town of Lassa in Borno State (from where it derived its name), the disease is endemic in Edo, Nasarawa and Plateau States.

This recent outbreak has exposed Nigeria’s easy susceptibility to preventable, but high mortality diseases. The devastating effect of Lassa fever is felt year after year. Although the Federal Ministry of Health has stepped in by providing drugs for the affected States, more needs to be done, especially in the areas of prevention. Health workers who should be in the forefront of fighting the epidemic are at greater risk of getting infected. Out of 40 deaths that have been reported are six Health Workers – two Doctors and four Nurses. This is enough reason for the government to also protect their lives through the provision of essential kits such as gloves and surgical masks needed by them to do their work without unduly exposing themselves.

In spite of the mortality rate ranging from 15 percent to 45 percent in some case, the disease could be treated by prompt medical intervention. Even though it starts with fever, it is always safe for diagnosis for Lassa fever to be considered in febrile conditions so that treatment could be administered before the situation gets out of hand. Although there is no vaccine as at now to prevent Lassa fever, it is heartwarming that many patients who survive it can build immunity against future attacks.

REFERENCES

Frame JD, Baldwin JM, Gocke DJ, Troup JM (1 July 1970) “Lassa fever, a new virus disease of man from West Africa. Clinical description and pathological findings”.

“SIGA Passes First Hurdle with Lassa Fever Antiviral St-193” (Press release).