Lassa fever also known as Lassa haemorrhagic fever (LHF) is an acute viral illness that occurs in West Africa. Though first described in the 1950’s, the illness was discovered in 1969 when two missionary nurses died in Nigeria. The virus is named after the town in Nigeria where the first cases occurred. It was first discovered in a town called Lassa in Borno State in the North Eastern part of Nigeria. The virus a member of the virus  family, Arenaviridae, is a single-stranded RNA virus and is zoonotic, or animal borne. Lassa fever is endemic in parts of West Africa including Sierra Leone, Guinea and Nigeria; however, other neighbouring countries are also at risk, as the animal vector for Lassa virus, the “multimammate rat” (Mastomys natalensis) is distributed throughout the region. In 2009, the
first case from Mali was reported in a traveller living in Southern Mali; Ghana reported its first case in late 2011. Isolated cases have also been reported in Cote d’lvoire and Burkina Faso and there is serologic evidence of Lassa virus in Togo and Benin.
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 known that 10% -16% of people admitted to hospital every year have Lassa Fever, which indicates the serious impact of the disease on the
population of this region. 
Symptoms of Lassa fever The incubation period of Lassa fever ranges from 2-21 days. The onset of the disease when it is symptomatic is usually gradual, starting with fever, general weakness and malaise. One might think it is ordinary malaria (therefore any fever must be treated with index of suspicion of Lassa fever during an outbreak, until proven otherwise). After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough and abdominal pain may follow. In severe cases facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop.
Protein may be noted in the urine, shock, seizures, tremor, disorientation and coma may be seen in the later stages. Deafness occurs in 20% of patients who survive the disease. In half of these cases, hearing returns partially after 1-3 months. Transient hair loss and gait disturbance may occur during recovery. Death usually occurs within 14days of onset of fatal cases.
Humans usually become infected with Lassa virus from exposure to urine or faeces of infected Mastomys rats. Lassa virus may also be spread between humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person infected with Lassa fever. There is no epidemiological evidence supporting airborne spread between humans.
Person-to-person transmission occurs in both community and healthcare settings, where the virus may be spread by contaminated medical equipment, such as re-used needles. Sexual transmission of Lassa virus has been reported.
Lassa fever occurs in all age groups and both sexes.
Persons at greatest risk are those living in rural areas where Mastomys rats are usually found, especially in  communities with poor sanitation or crowded living conditions. Health workers are at risk of caring for Lassa fever patients in the absence of proper barrier nursing and infection prevention and control practices.
Prevention and control
Prevention of Lassa fever relies on promoting good “community hygiene” to prevent rodents (rats) 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. Because Mastomys (rats) are so abundant in endemic areas, it is not possible to completely eliminate them from the environment. Family
members should always be careful to avoid contact with blood and body fluids while caring for sick persons. On rare occasions, travellers from areas where Lassa fever is endemic export the disease to other areas.
Although malaria, typhoid fever and many other tropical infections are much more common, the diagnosis of Lassa fever should be considered in febrile patients returning from areas where there is an outbreak of Lassa fever.

The antiviral drug Ribavirin seems to be an effective treatment for Lassa fever if given early on in the course of  clinical illness. There is no evidence to support the role of Ribavirin as post-exposure prophylactic treatment for Lassa fever. There is currently no vaccine that protects against Lassa fever.
The Current Situation
Since the beginning of 2018, Nigeria has recorded 16 deaths from 61 confirmed cases of Lassa fever across the country. The Nigeria centre for Disease control, NCDC in a press statement on Wednesday 24th January 2018 said a total number of 107 suspected cases have been recorded in ten states across the country. The states are Ebonyi, Edo, Ondo, Bauchi, Nasarawa, Anambra, Benue, Kogi, Imo and Lagos. According to the health agency, as at January 21, ten out of the 61 confirmed cases were health care workers from four states Ebonyi-7, Nassarawa-1, Kogi-1 and Benue-1 out of which four are now secondary victims who get infected while treating patients with the disease. It is worthy of note that hand washing
should also be practiced frequently.
Lassa fever is an acute viral haemorrhagic illness of 2-21days of incubation period that occurs in West Africa.
The Lassa virus is transmitted to humans via contact with food or household items contaminated with rodent (rat) urine or faeces.
Person-to-person infections and laboratory transmission can also occur, particularly in hospitals lacking adequate infection
prevention and control measures.
Lassa fever is known to be endemic in Benin, Ghana, Guinea, Liberia, Mali, Sierra Leone and Nigeria but probably exists in other West African countries as well.
The overall case fatality rate is 10% observed, case-fatality rate among patients hospitalized with severe cases of Lassa fever is 15%.
Early supportive case with rehydration and symptomatic treatment improves survival.
About 80% of people who become infected with Lassa virus have no symptoms. 1 in 5 infections result in severe disease where the virus affects several organs such as the liver, spleen and kidneys.
Content source centres for disease control and prevention –
World Health Organisation (WHO) –
Nigeria Centre for Disease Control publications (NCDC)
Federal Ministry of Health (FMOH) publications-Nigeria.
Dr David Obasi Ukoha (MBBCH, DFM, MHPM, FAGP, FRSTMH,
Deputy Director Hospital Services
Directorate of Health Services
National Assembly, Abuja

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