Lassa Fever Outbreak in Nigeria and Ongoing Health Risks

• A large outbreak of Lassa Fever has occurred in Borno State, Nigeria.
• No preventative medicine or vaccine exists to treat the disease.
• Up to 20 per cent of those hospitalised by the disease are killed, with a total mortality rate around one per cent of those infected.

Health: An outbreak of Lassa fever centred on the Borno State region of Nigeria has led to 1081 suspected infections between 01 and 25 February 2018. Of these, 317 cases have been confirmed, and the fatality rate stands at 22 per cent. This outbreak is the first one reported in Borno state for decades and is spreading at a rate faster than any previously recorded outbreak, it is also the largest outbreak of Lassa fever ever reported in Nigeria. Both national and international medical agencies, including the World Health Organisation (WHO), are investigating the outbreak. Recent warfare and a large number of displaced persons throughout Borno state are likely to be contributing factors.

The virus is responsible for smaller outbreaks across West Africa on a regular basis, with the WHO estimating that it is responsible for 3,000 – 5,000 deaths per year. Sierra Leone, Liberia, and Guinea are routinely impacted by the disease.

Lassa fever is, like Ebola, a viral haemorrhagic fever but is not as easily transferred and less deadly. Approximately 80 per cent of those infected suffer slight or no symptoms. The remaining 20 per cent who suffer complications are likely to experience life-changing debilitations, such as hearing loss, or in some cases death.

Symptoms are likely to manifest between one and three weeks from the initial infection. Mild symptoms include a light fever, general weakness, and a headache. More serious cases involve haemorrhaging from areas such as the eyes, gums, or nose; respiratory distress, repeated vomiting, facial swelling, chest or back pain, and shock. Hearing loss, shaking, and encephalitis may also occur. Death typically occurs two weeks after symptoms show, due to multiple organ failure.

Some level of hearing loss occurs in approximately 30 per cent of cases, regardless of the severity of other symptoms. Women in the third trimester of pregnancy are significantly more likely to suffer fatal complications of the disease, and death occurs in 95 per cent of infections of pregnant women.

The virus is harboured in the multimammate rat, a species indigenous to the region, and found across the full spectrum of environments, from savannah to dense forest. The species also frequently colonises human residences as a ready source of shelter and food.

The virus is carried in the rats’ bodies and may also be present in urine or faeces. Combined with their close co-habitation with humans, their scavenging behaviour means that contaminated food or poor sanitary procedures are the cause of many initial infections. A risk is also present from microscopic aerial particles which may be inhaled whilst sweeping or cleaning away dry rat droppings. Handling the carcass of a dead rat may also lead to contamination or infection. In some regions dealing with malnutrition and poverty, the rats are also consumed by humans and, if incorrectly cooked, the virus may be transferred directly into the human digestive system.

Human-to-human transmission may occur due to direct contact with the blood, tissue, or excretions of an infected individual. Due to this, a major risk is posed in a healthcare setting, particularly if access to hygiene supplies is limited, or if the care takes place in an improvised or home-care setting. Casual, skin-to-skin contact cannot spread the virus.

The most effective treatment strategy presently available post-infection is the intra-venal use of ribavirin, an anti-viral drug, as soon as symptoms are detected. Additional treatments include maintaining the patient’s fluid levels and treating any complications or follow-on infections.

Preventative measures remain the most effective means of avoiding the disease and its related complications. All food should be stored in rodent proof containers, and residences should be thoroughly cleaned to discourage rodents from entering. Baiting and trapping rodents around homes may also minimise risk of infection. The presence of cats or other predators may also assist in driving rodents away from inhabited areas. The spread of Lassa can be prevented in the medical setting by the use of isolation or barrier nursing methods. Healthcare providers should use protective clothing to avoid contact with bodily fluids from the infected, and sterilisation procedures should be vigorously enforced.