Lassa Fever: What You Need To Know

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You might have heard of the recent Lassa fever outbreak in some parts of Nigeria. One of our bloggers, Dr Adepoju, shares more insight about the illness, its preventive and curative measure. Please read and share the link with friends and colleagues!

VENTURES AFRICA – The illness was first discovered in 1969 following the tragic death of two missionary nurses in northern Nigeria. Lassa fever belongs to a diverse group of animal and human illnesses that are collectively known as viral hemorrhagic fevers. It is caused by Lassa fever virus, an RNA virus that was named after Lassa town in Borno state, Nigeria, where the fever was first described. Outbreaks of the disease in varying severities have been reported in Nigeria, Guinea, Central African Republic, Liberia and Sierra Leone, Mali, Senegal and Democratic Republic of the Congo.

Lassa fever is an animal infection that is accidentally transmitted to man. It spreads to man from rodents (rats), specifically multi-mammate rats (Mastomys natalensis), which is the most common rodent in equatorial (West and Central) Africa. The specie is found in rural and urban households and eaten as a delicacy in some African communities. The fever is asymptomatic in infected rats but could be unnoticeable or fulminant (sudden and severe) in human victims. According to Associated Press (AP), estimated 100,000 – 300,000 infections occur every year in West Africa, with approximately 5,000 deaths.

The virus is shed in urine and feces of rodents, and could be aerosolized and deposited on foods that are kept in rodent-infested residences. Inhalation of aerosols is the most significant means of exposure in addition to ingestion of infective materials. The virus could also be contracted through broken skin and exposed mucous membranes. Interpersonal transmission is also common, presenting a nosocomial (hospital-acquired) disease risk for healthcare workers. Although transmission via sexual contact has been demonstrated, the frequency of transmission has not been established.

After gaining entry, the virus infects almost every tissue in the human body. It starts with the mucosa, intestine, lungs and urinary system, and then progresses to the vascular system (blood). At this stage, it presents an array of symptoms.

According to US Centers for Disease Control and Prevention (CDC), symptoms of Lassa fever occur 1 – 3 weeks after contracting the virus. They include fever, pain behind the chest wall, sore throat, back pain, cough, abdominal pain, vomiting, diarrhoea conjunctivitis, facial swelling and mucosal bleeding. If the disease is left untreated, neurological (nervous system – brain, spinal cord and nerves) involvement is imminent. These include hearing loss, tremors and encephalitis. The kidneys could also be affected.

Deafness is the most common complication of Lassa fever and it occurs in about one-third of all cases. It could be temporary but in many cases, it is often permanent. Deafness may develop in mild as well as in severe cases. 15 – 20 percent of Lassa fever patients on hospital admission die from the disease. The mortality rate is particularly high for women in the third trimester of pregnancy, and about 95 percent of foetuses die in the uterus of infected pregnant mothers.

People at risk are those who live in houses and/or areas with large number of rats, and hospital workers who don’t take adequate protective measures. Because the symptoms of Lassa fever are varied and nonspecific, clinical diagnosis is often difficult. However, laboratory diagnosis is the gold standard. The method of choice is enzyme-linked immunosorbitent assay (ELISA) – a method that is also used to confirm HIV diagnosis. Other available methods are immunofluorescence, immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The later is primarily a research tool.

Unlike AIDS, Lassa fever is curable. The antiviral drug – Ribavirin, has been used successfully but it should be given early in the course of the illness. Supportive care (fluid and electrolyte balance, oxygenation and blood pressure) is also necessary for full recovery. Furthermore, co-infections should be diagnosed and treated appropriately.

It is worthy to note that vaccines against Lassa fever are not yet available hence adequate education and enlightenment are needed. In addition, rat traps and other similar efforts could significantly reduce or totally eliminate rodent infestation. Foods should be kept in well covered containers.

When taking care of patients with Lassa fever, isolation precautions or barrier nursing methods could help prevent nosocomial transmission. The precautions include wearing proper protective clothing including masks, gloves, gowns, and goggles; applying infection control measures, such as complete equipment sterilization; and isolating infected patients until they’ve fully recovered.