Mastomy rat

Lassa fever is an acute illness that occurs predominantly in west Africa. Though it was first described in 1950s, the illness was not discovered until 1969 when two missionary nurses died in Nigeria, West Africa. It was later found that the cause of the illness was found to be a virus which was later called Lassa virus, named after the town in Nigeria where the first cases originated. The virus, a member of the virus family Arenaviridae, is a single-stranded RNA virus and is zoonotic (i.e the virus is carried by animal called mastomy rat)

In areas of Africa where the disease is common, Lassa fever is a significant cause of morbidity and mortality. Though the mastomy rat that carry the virus is found throughout West Africa, the disease is common in Guinea, Nigeria, Sierra Leone and Liberia. Lassa fever is mild or has no observable symptoms in about 80% of people infected with the virus, the remaining 20% have a severe disease affecting virtually all the organs of the body for example, liver, spleen, kidney, ear, brain e.t.c.

How many people become infected?

It is estimated that in West Africa an estimated 300,000 to 500,000 cases of infection occur per year, with approximately 5,000 deaths. Unfortunately, such estimates are crude, because not all cases are being reported. The disease is especially severe late in pregnancy, with maternal death and/or fetal loss occurring in greater than 80% of cases during the third trimester.

How do humans get Lassa fever?

There are a number of ways in which humans can contact the virus. The Mastomys rodents usually shed the virus in urine and excreta. Therefore, humans can contact the virus through direct contact with these materials, through touching objects or eating food contaminated with these materials, or through cuts or sores. Because Mastomys rodents often live in and around homes and scavenge on human food remains or poorly stored food, transmission of this sort is common. Finally, because Mastomys rodents are sometimes consumed as a food source, infection may occur 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 into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus. The virus cannot be spread through casual contact (including 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 modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles. It can also be contacted through sexual means.

What are the symptoms of Lassa fever?

The disease takes a gradual course, starting with fever, general weakness, and malaise. After a few days, headache, sore throat, muscle pain, back pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal may follow. Severe cases may progress to show facial swelling, bleeding from mouth, nose, vagina or gastrointestinal tract, and low blood pressure. Shock, seizures, tremor, disorientation, and coma may be seen in the late stages.

The incubation period of Lassa fever ranges from 6-21 days. This means that the period of time between which a person contact the virus and when he or she will develop these features is 1 – 3 weeks.

Treatment of Lassa fever

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. This drug should not be taken except with the approval of a Medical Doctor.

How is Lassa fever prevented?

Primary transmission of the Lassa virus from its host to humans can be prevented by avoiding contact with Mastomys rodents, Prevention of Lassa fever in the community centers on promoting good “community hygiene” to discourage rodents from entering homes 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. Eating of rodents should be avoided. Rat traps in and around homes can help reduce rodent populations. Keeping cats at home will also reduce contact with the rodents as cats has been known to kill rats. Other methods of killing rats at home should also be employed.

Other effective measures include storing grain and other foodstuffs in rodent-proof containers and maintaining clean households.

When caring for patients with Lassa fever, further transmission of the disease through contact with the affected person can be avoided by taking preventive precautions against contact with patient secretions. 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.

In conclusion, Lassa fever just like HIV/AIDS is real, thus all hands must be on deck to ensure that this infection is controlled.

World Health Organization (WHO)
Centre for disease control (CDC)

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