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The Return Of Lassa Fever



The Nigeria Centre for Disease Control (NCDC) recently alerted the nation to a fresh outbreak of Lassa fever in some states of the federation, including Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Plateau, Taraba and the Federal Capital Territory (FCT). According to the NCDC, 16 deaths from 60 cases of the disease have been confirmed while 590 out of 593 contacts are currently under watch in the eight affected states. This current outbreak is coming on the heels of the Lassa fever international conference held recently in Abuja to mark the 50th anniversary of the discovery of the disease in the country.

Lassa fever, an acute viral haemorrhagic fever that is extremely virulent and often infectious, occurs very frequently in different parts of Nigeria and affects approximately 100,000 to 500,000 persons per year in West Africa. The illness was first discovered in Lassa, Borno State, from where it took its name.

The disease is caused by the Lassa fever virus, a single strained ribonucleic acid  belonging to the arenaviridae family. It is transmitted to humans from contacts with food or household items contaminated with rodent excreta. The incubation period for Lassa fever varies from 6-12 days. It is symptomatic and usually characterised by fever, myalgia, nausea, vomiting, sore throat, abdominal and chest pains, and the illness may progress to more serious symptoms including haemorrhaging, neurological problems, hearing loss, tremors and encephalitis.

Accurate and rapid diagnosis of Lassa fever is especially challenging due to the non-specific clinical presentation, the high degree of Lassa virus genetic diversity observed in West Africa, and the biosafety concerns regarding laboratory testing for high consequence pathogens. While there are many diagnostic assays for Lassa virus, there is  currently no timely, validated pan-Lassa virus assay available to both capture the diversity among viral strains and provide a diagnosis at any time during the clinical course of illness.

Commenting on the recent outbreak in the country, the World Health Organisation (WHO) officer in charge of Nigeria, Dr. Peter Clement, said that in response to the outbreak, WHO had reorganised its staff to provide assistance to each of the response pillars and had also directed field offices to assist in outbreak investigation, coordination and response activities at the state level.

The global health body, according to Dr. Peter, “is supporting coordination, enhanced surveillance, contact tracing, and risk communication” in addition to mobilising experts to support case management and detailed epidemiological analysis to monitor the situation in the affected states.

For now, there is no vaccine for preventing Lassa fever and since the disease presents no specific symptoms, clinical diagnosis is often difficult, especially at the onset of the disease. Accurate diagnosis therefore can be assisted with differential laboratory testing as well as clinical observation. Due to the absence of a vaccine against the virus and the impractical control of the rodent host population, control measures are limited to keeping rodents out of homes and food supplies and also maintaining proper personal hygiene. Using these rodents as food (meat) should be discouraged. Enlightenment and awareness of the public on risk factors associated with the spread of the disease is important for prevention. Protective measures should be put in place to reduce human infection. Infected persons should be isolated and their body fluids and excrement properly disposed. Healthcare workers should take proper precautions in order to curtail nosocomial spread of the disease through the use of Personal Protective Equipment (PPE).

It is the opinion of this newspaper that the current outbreak of Lassa fever in the country can be controlled effectively by adopting proper and standard precautions in hospitals and communities. Educating the public on the mode of transmission of the virus and the need for proper hygiene and environmental sanitation should be emphasised.

Also, given the risk of person-to-person virus spread via bodily fluids, laboratory staff should be aware of the risk of Lassa virus when processing potentially infectious specimens. Poor sample storage and handling may pose a safety hazard to laboratory staff as well as decrease the sensitivity of diagnostic assays. The World Health Organisation guidelines for the collection, storage and handling of specimens for Ebola virus testing should be followed when testing for Lassa virus. It is also important for primary healthcare offices at the state and local government levels to increase awareness on the prevalence and preventive measures of the disease. Also, people should be educated to keep their homes clean as rodents are attracted to a dirty environment.                                   


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