LASSA FEVER: What we need to know

There is outbreak of Lassa fever in Nigeria. As at the time of writing this report, 159 suspected cases (including 82 deaths) have been reported in 19 states.


lassa-feverLassa fever is an acute viral haemorrhagic illness caused by the Lassa virus- a single-stranded RNA virus of the family Arenaviridae. It was first described in 1969 in the town of Lassa, in Borno State, Nigeria, when two missionary nurses died from the disease in the region. Lassa fever is a zoonotic (animal-borne) disease- human beings become infected from contact with infected animals. The animal reservoir (host) of Lassa virus is the “multimammate rat”, a rodent of the genus Mastomys (Mastomys natalensis). The rats do not become ill when infected by the virus, but can shed the virus in their urine and faeces. Human beings become infected with the virus due to contacts with urine or faeces of infected Mastomys rats. The virus may also spread among humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person with Lassa fever (Human-to-Human transmission). This is particularly common in communities with poor sanitation and crowded residence, and in healthcare settings with poor control and prevention of infectious diseases. Although hospital staffs caring for infected persons may not be at great risk provided standard barrier nursing, sterilization and infection control practices are in place. There is yet any evidence to support airborne spread of the disease, but sexual transmission has been reported in some settings.

Lassa fever is known to be endemic in West African countries, where the Mastomys rats are widely distributed, particularly in Benin, Guinea, Liberia, Sierra Leone and Nigeria. The reported CFR is 1%, but may be as high as 15% for severe cases of Lassa fever. Patients often respond well with prompt supportive care, adequate rehydration, and symptomatic management.


Basic Symptoms and Clinical Course

Reports show that 80% of infected persons generally have mild or no symptoms (and are often undiagnosed), with only about 20% of infections resulting in severe disease- affecting multiple body organs, including the liver, spleen and kidneys. Symptoms generally begin about 1-3 weeks (6-21 days) following first contact with the virus. Mild symptoms include slight fever, general malaise and body weakness, and headaches. For a progressing disease, severe headaches, sore throat, cough, chest pains, muscle aches, nausea, vomiting, and diarrhoea, may follow after few days. Severe symptoms include bleeding from the gums, eyes or nose, menorraghia (increased menstrual flow), facial swelling, breathing difficulties and cough, pain in the chest, back, and abdomen, repeated vomiting, diarrhoea (may be bloody), hematuria (blood in urine), low blood pressure and shock. Deafness, which in many cases may be permanent, is the most common complication of Lassa fever. Other neurological complications have also been reported, including tremors, encephalitis (inflammation of the brain), seizures, disorientation, and coma. Death may occur within two weeks after onset of fatal illness due to multiple organ failure.


Prevention and Control

When Lassa fever is confirmed in a community, immediate isolation of affected persons, adequate protection and control practices, and rigorous contact tracing have been found to be helpful.

Prevention of Lassa fever centres on promoting good hygiene and sanitation measures within communities to prevent rats from entering homes. Other measures include storing grains and food stuffs in rodent-proof containers, disposing waste and garbage far from homes, cutting grasses and maintaining clean households. Domestic cats may also be helpful. However, it may not be possible to completely eliminate Mastomys rat in endemic areas, as they could be very many in such areas. Family members and relatives also need to avoid contact with blood and body fluids of infected persons when caring for them. Regardless of the presumed diagnosis, health workers are to maintain strict infection prevention and control measures during outbreaks. International standards for infection prevention and control include basic hand hygiene, respiratory hygiene, use of personal protective equipment (a face shield or a medical mask and goggles to block splashes or other contact with infected materials), safe injection practices, and safe burial practices. Laboratory workers should also take extra caution when handling specimen.


Diagnosis and Treatment

Diagnosis is quite difficult to establish based on clinical signs and symptoms, as presentations are just like other viral hemorrhagic fevers, eg. the Ebola virus disease. Definitive diagnostic tests should be conducted in a suitably equipped specialized laboratory with standard protective measures strictly adhered to. The Irrua Specialist Teaching Hospital, Edo State, is the main specialty health centre for viral hemorrhagic fevers in Nigeria.

The only available drug for Lassa fever is Ribavirin, and is only effective when administered at the early stages of infection (within first 6 days). As noted above, immediate supportive care, rehydration and symptomatic treatment greatly improves survival. There is no vaccine currently available that protects against Lassa fever in humans. The apparent absence of functional antibodies during acute infection has affected researches related to vaccines development.



There is no need to panic. The University Health Centre has an Infectious Diseases Control Unit. The Ogun State government has also issued a statement confirming that there is yet any case reported in the state. The following telephone lines – 09099140121 and 09099140122 – have been specially dedicated to report any outbreak in the state. The general public, health-care workers and/or doctors in local private hospitals seeing a patient suspected to have Lassa fever should immediately contact the nearest tertiary health centre for appropriate management. The Nigerian Centre for Disease Control (NCDC) is co-ordinating a nationwide response and daily reporting to the health ministry. Generally, efforts should be directed at decreasing rodents’ populations in and around our homes, as this is the most important primary preventive option!
Dr. Davies Adeloye
Demography and Social Statistics, and
The e-Health Research Cluster
Covenant University, Ota, Nigeria.


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