Lassa fever is an acute viral illness that occurs in West Africa. The illness was discovered in 1969 when two missionary nurses died of it in Nigeria. The Lassa fever virus (LFV) was named after the town where the first cases occurred, Lassa a village in Borno State located in the North Eastern region of Nigeria.

The virus, a member of the virus family Arenaviridae, is a single-stranded RNA virus and is zoonotic, or animal-borne. In areas of Africa where the disease is endemic (that is, constantly present), Lassa fever is a significant cause of morbidity and mortality. While Lassa fever is mild or has no observable symptoms in about 80% of people infected with the virus, the remaining 20% have a severe multisystem disease. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50%. Lassa fever is an endemic disease in portion of West Africa and is recognized in Guinea, Liberia, Sierra Leone and Nigeria. However, because the rodent species which carry the LFV are found throughout West Africa, the actual geographic range of the disease may extend to other countries in the region.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. Approximately 15%-20% of patients hospitalized for Lassa fever die from the illness. However, overall only about 1% of infections with Lassa virus result in death. The death rates are particularly high for women in the third trimester of pregnancy, and for fetuses, about 95% of which die in the uterus of infected pregnant mothers.

The first case of the current outbreak was reported in Bauchi state in November, 2015. It has now extended to at least 17 states claiming at least 63 lives in the process.

Symptoms of Lassa fever typically occur 7 – 21 days after the patient comes in contact with the LFV. These include fever, retro-sternal pain (pain behind the chest wall), sore throat, abdominal and back pain, cough, vomiting, diarrhea, conjunctivitis (red eyes), facial swelling, protein in the urine and mucosal bleeding. Permanent hearing loss, tremors and encephalitis have also been described.

There are a number of ways in which the LFV may be spread to humans. The reservoir, or host, of LFV is a rodent known as the “multi-mammate rat” which shed the virus in their urine and droppings. LFV can be transmitted through direct contact with these materials, through contaminated objects or food, or through cuts or sores. Infection can also occur when a person inhales tiny dust particles in the air contaminated with infected rodent waste. LFV may also spread person-to-person. This type of transmission occurs when an uninfected person comes in contact with the virus in the blood, tissue, secretions, or excretions of an infected individual.

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.

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. However, the wide distribution of Mastomys in Africa makes complete control of this rodent reservoir impractical. 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.

Further educating people in high-risk areas about ways to decrease rodent populations in their homes will aid in the control and prevention of Lassa fever. Other challenges in developing countries include increasing the number of diagnostic centres and isolation units in designated hospitals and putting in place national protocols on how to handle high risk patients and identified cases. Also developing more rapid diagnostic tests and increasing the availability of the only known drug treatment, ribavirin. Research is presently under way to develop a vaccine for Lassa fever.

Source:http://www.untoldafrique.com/2016/02/04/facts-on-lassa-fever/

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