Basically, Lassa fever is a viral haemorrhagic fever transmitted by rats. The disease has been known since the 1950s, but the virus was not identified until 1969, when two missionary nurses died from it in the town of Lassa in Nigeria.
In this post, we take a look at Lassa fever in Nigeria, its outbreaks and preventive solutions.
Lassa Fever in Nigeria: History, Outbreaks & Prevention
Lassa fever is found predominantly in West Africa and it has been linked to thousands of deaths since it was discovered. The disease is endemic in Ghana, Guinea, Mali, Benin, Liberia, Sierra Leone, Togo and Nigeria.
Over the years, Lassa fever has killed several thousands of people each year in these West African countries. With access to the region improving, the opportunity, and the need, to improve our understanding of this disease are increasing
Lassa fever is transmitted to humans via contact with food or household items contaminated with rodent urine or faeces. Also, person-to-person infections and laboratory transmission may occur.
Early supportive care with rehydration and symptomatic treatment improves survival. Also, the antiviral drug, ribavirin seems to be an effective treatment for Lassa fever if given early on in the course of clinical illness. However, there is no evidence to support the role of ribavirin as post-exposure prophylactic treatment for Lassa fever.
Between January 1 and February 25, 2018, 1081 suspected cases and 90 deaths were reported from 18 states (Anambra, Bauchi, Benue, Delta, Ebonyi, Edo, Ekiti, Federal Capital Territory, Gombe, Imo, Kogi, Lagos, Nasarawa, Ondo, Osun, Plateau, Rivers, and Taraba).
During this period, 317 cases have been classified as confirmed and eight as probable, including 72 deaths (case fatality rate for confirmed and probable cases = 22 percent). A total of 2845 contacts have been identified in 18 states.
Following the outbreak of Lassa fever, there has been establishment of case management centers in four states of the country (Anambra, Abakaliki, Edo, and Ondo States).
Additionally, health care professionals working in these centers are trained in standard infection control and prevention (IPC) as well as in the use of personal protective equipment (PPE).
The suspected cases and deaths reported in community settings are also being actively investigated by the field teams and contacts are being followed up. There are operational laboratories for testing samples for Lassa fever by polymerase chain reaction (PCR).
The World Health Organization continues to support the outbreak response, mainly in the domains of enhanced surveillance, contact tracing, strengthening of diagnostic capacity and risk communication.
The public health response to Lassa fever in Nigeria has been quite prompt and robust. Following the reports, a national Lassa fever Emergency Operations Centre (EOC) was activated in Abuja on 22 January and continues to coordinate response activities in collaboration with WHO and other partners.
Also, a team of Nigerian Centre for Disease Control (NCDC) staff and Nigeria Field Epidemiology and Laboratory Training Program (NFELTP) residents were deployed to respond to the Ebonyi, Ondo, and Edo outbreaks.
The three most affected states of Edo, Ondo and Ebonyi have dedicated Lassa fever treatment units and ribavirin is available for treatment of confirmed cases. Additionally, NCDC is collaborating with a non-governmental organization, the Alliance for International Medical Action (ALIMA), to conduct an assessment of treatment units.
There is also enhanced surveillance is ongoing in states with an active outbreak and state line lists of cases are being uploaded to a national level database, a viral haemorrhagic fever management system.
The NCDC has supplied Irrua Specialist Teaching Hospital and Federal Medical Centre Owo with tents and beds to increase in-patient capacity. Also, staffs from Irrua Specialist Teaching Hospital are providing clinical case management advice to other hospitals with suspected cases, and a 24-hour Lassa fever case management call line has been established.
It was reported that 14 health care workers that were not working in Lassa fever case management centers were infected. This highlights the urgent need to strengthen infection prevention and control practices in all health care setting for all patients, regardless of their presumed diagnosis. Given the high number of states affected, the clinical management will likely happen in health centers that are not appropriately prepared to care for patients affected by Lassa fever and the risk of infection in health care workers will increase.
The reporting of confirmed cases in different parts of the country and porous borders with neighbouring countries indicate a risk of spread nationally and to neighbouring countries. An overall moderate level of risk remains at the regional level. Public health actions should be focused on enhancing ongoing activities including surveillance, contact tracing, laboratory testing, and case management. Greater coordination and information sharing regarding Lassa fever cases and contacts with Benin would also contribute to rapid detection and response to cross-border spread of the outbreak.
According to the WHO, the prevention of Lassa fever relies on community engagement and promoting hygienic conditions to discourage rodents from entering homes. In healthcare settings, staff should consistently implement standard infection prevention and control measures when caring for patients to prevent nosocomial infections.
Travellers from areas where Lassa fever is endemic can export the disease to other countries, although this rarely occurs. The diagnosis of Lassa fever should be considered in febrile patients returning from West Africa, especially if they have been in rural areas or hospitals in countries where Lassa fever is endemic. Health care workers seeing a patient suspected to have Lassa fever should immediately contact local and national experts for guidance and to arrange for laboratory testing.
Also, health care workers should note that Lassa fever presents initially like any other disease causing a febrile illness such as malaria; consequently, they are advised to practice standard precautions at all times, maintaining a high index of suspicion. Rapid Diagnostic Test (RDT) must be applied to all suspected cases of malaria. When the RDT is negative, other causes of febrile illness including Lassa fever should be considered. Accurate diagnosis and prompt treatment increase the chances of survival.
As of 2018, three laboratories at Abuja, Irrua and Lagos are operational and testing samples for Lassa fever by polymerase chain reaction (PCR).
The phylogenetic evaluation of 49 viruses detected during the 2018 outbreak which was provided through ongoing collaborations between Irrua Specialist Teaching Hospital, Bernhard Nocht Institute of Tropical Medicine, African Center of Excellence for Genomics of Infectious Disease (ACEGID), and Redeemer’s University, has shown evidence of multiple, independent introductions of different viruses and viruses similar to previously circulating lineages identified in Nigeria. This is indicative that the main mode of transmission is through spillover from the rodent population, and limited human to human transmission.