Fifty years after the first outbreak of Lassa fever, the disease still continues to claim lives. VINCENT IKUOMOLA writes on why the country may not be able to exterminate the virus.
Lassa fever is an acute viral haemorrhagic illness that occurs in West Africa, after exposure to the urine or faeces of infected mastomys rats.
More than 80 per cent of Lassa fever cases are rodent-to-human transmission. Person-to-person transmission also occurs in both community and health-care settings.
It is one of the most ravaging diseases that have plagued the country, so recurrent that the disease seems to have become synonymous with Nigeria. Ironically, as the nation marks 50 years of the first discovery of the virus in a small town called Lassa in Borno State, there is an outbreak of the disease in some parts of the country. Though first outbreak of the disease was in the 1950s, the virus causing Lassa disease was not identified until 1969. The virus is a single-stranded RNA virus belonging to the arenaviridae Family. At the moment, there is no vaccine that protects against Lassa fever.
Lassa fever is also a zoonotic disease, meaning that humans become infected from contact with infected animals. The animal reservoir, or host, of Lassa virus is a rodent of the genus mastomys, commonly known as the “multimammate rat.” Although mastomys rats infected with Lassa virus do not become ill, they can shed the virus in their urine and faeces. About 80 per cent of people who become infected with Lassa virus in most cases have no symptoms. According to experts, one in five infections result in severe disease, where the virus affects several organs, such as the liver, spleen and kidneys.
Symptoms of Lassa fever
The onset of the disease, according to WHO, is usually gradual, starting with fever, general weakness, and malaise and most times, is fatal. After a few days, headache, sore throat, muscle pain, chest pain, nausea, vomiting, diarrhoea, cough, and abdominal pain may follow. In severe cases, facial swelling, fluid in the lung cavity, bleeding from the mouth, nose, vagina or gastrointestinal tract and low blood pressure may develop.
Protein may be noted in the urine. Shock, seizures, tremor, disorientation, and coma may be seen in the later stages. Deafness occurs in 25 per cent of patients who survive the disease. In half of these cases, hearing returns partially after one to three months. Transient hair loss and gait disturbance may occur during recovery.
The incubation period of Lassa fever ranges from six to 21 days. Death usually occurs within 14 days of onset in fatal cases. The disease is especially severe in pregnancy, with maternal death and/or fetal loss occurring in more than 80 per cent of cases during the third trimester.
Humans usually become infected with Lassa virus from exposure to urine or faeces of infected mastomys rats. Lassa virus may also be spread between humans through direct contact with the blood, urine, faeces, or other bodily secretions of a person infected with Lassa fever. There is no epidemiological evidence supporting airborne spread between humans. Person-to-person transmission occurs in both community and health-care settings, where the virus may be spread by contaminated medical equipment such as re-used needles. Sexual transmission of Lassa virus has been reported.
Lassa fever occurs in all age groups and both sexes. Persons at greatest risk are those living in rural areas where mastomys are usually found, especially in communities with poor sanitation or crowded living conditions. Health workers are at risk of caring for Lassa fever patients in the absence of proper barrier nursing and infection prevention and control practices. Because the symptoms of Lassa fever are so varied and non-specific, clinical diagnosis is often difficult, especially early in the course of the disease.
Lassa fever is difficult to distinguish from other viral haemorrhagic fevers, such as Ebola virus disease, as well as other diseases that cause fever, including malaria, shigellosis, typhoid fever and yellow fever.
Primary transmission of Lassa virus from its host to humans can be prevented by avoiding contact with mastomys rodents, especially in the geographic regions where outbreaks occur. Putting food away in rodent-proof containers and keeping the home clean help to discourage rodents from entering homes. This speaks greatly to the promotion of good “community hygiene” to discourage rodents from entering homes. Effective measures include storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, maintaining clean households and keeping cats. Because mastomys are so abundant in endemic areas, it is not possible to completely eliminate them from the environment. Family members should always be careful to avoid contact with blood and body fluids while caring for sick persons.
The virus has become endemic in West Africa. Nigeria, between January and last May, experienced the largest outbreak of the disease ever recorded. The outbreak spread to 18 states with 1,081 suspected cases and 90 reported deaths; 317 of the cases and 72 deaths were confirmed as Lassa. The upsurge in the cases recorded placed Nigeria on high international surveillance alert raising concerns over the emergence of the strain of the disease and transmission rate.
According to weekly epidemiological report from the Nigeria Centre for Disease Control (NCDC), there have been 57 deaths caused by Lassa fever in this year alone, with a fatality rate in confirmed cases at 20.7 per cent. From January 1 to February 3, 2019, a total of 731 suspected cases had been reported from 19 States. Of these, 275 were confirmed positive, three probable and 453 negative (not a case). So far, the outbreak has spread to 19 states, namely Edo, Ondo, Bauchi, Nasarawa, Ebonyi, Plateau, Taraba, FCT, Adamawa, Gombe, Kaduna, Kwara, Benue, Rivers, Kogi, Enugu, Imo, Delta and Oyo. They have recorded at least one confirmed case across 51 local government areas.
Health workers were not also spared by the outbreak, with nine already affected in four states, namely Ebonyi (one), Ondo (two), Enugu (one) and Edo (five) with one death in Enugu.
This scenario paints a picture of helplessness of a country to contain the disease which is spreading fast like a wide fire, leaving behind heavy casualties. This has forced WHO regional office for Africa to raise concerns.
“We are concerned by the high number of cases so early in the Lassa fever season, which is expected to last another four more months. WHO is working with the health authorities in the five-affected countries to ensure health workers have the capacity to detect cases and we are monitoring the regional spread of the disease,” said Dr. Ibrahima Socé Fall, Regional Emergencies Director at WHO regional office for Africa.
For Nasarawa State Governor Tanko Al-Makura, the outbreak of the disease and its fatality rates were unacceptable. Almakura, a survivor of the fever, lost a son while he and another suffer from disability.
He contracted the disease in 1990 and that made him deaf for 20 years before he had a cochlear implant. The governor said he lost his first son to the fever nine years after his wedding, the second son survived but with the burden of the side effects of the virus, neurological problems, especially hearing loss. Al-Makura said he got infected when he was bitten on his finger while trying to prevent his then sick son from biting his tongue. He said he later fell sick with severe headache, seizures, cough, stomachache and erratic breathing.
According to him, it took the intervention of a foremost virologist and head of the National Lassa Fever Committee, Prof. Oyewale Tomori, who came to visit him at the Jos University Teaching Hospital (JUTH), Plateau State, to be saved.
Al-Makura said Tomori immediately instructed that he should be taken to EKO Hospital in Ikeja, Lagos and his blood sample sent to the Centre for Disease Control in Atlanta, Georgia, United States. The governor was diagnosed positive after two weeks.
“I stand as a product of the tragedy of Lassa fever. I was deaf and had to live with that for 20 years. I was using hearing aid until I had cochlear implant that mechanically processes the sound. I endured a certain measure of deafness. It was the same with my son who survived. I consider myself very lucky. I have survived to tell my story,” he said.
The governor expressed his regret that 50 years after the first outbreak, people were still dying from the fever, suggesting that the country has not done enough to contain the disease. However, the government said there was no need for panic, arguing that it has initiated measures to combat response to the disease.
Besides, given the increase in reported cases of Lassa fever, the NCDC has activated an emergency operations centre to coordinate the response.
According to the NCDC Director-General, Dr Chikwe Ihekweazu, the Federal Government has been providing support to states, including emergency supplies and deployment of rapid response teams (RRT) in preparation for this year’s emergency phase.
He said the RRTs would work with states in response coordination, contact tracing, case management, risk communication and strengthening infection prevention and control practices.
He advised the public to focus on its prevention by practising good personal hygiene and proper environmental sanitation, urging the people to take effective measures by storing grain and other foodstuffs in rodent-proof containers, disposing of garbage far from the home, maintaining clean households, and other measures to discourage rodents from entering homes.
The NCDC boss said a developing a vaccine to curb the disease was necessary due to its high transmission and case fatality rate. The Minister of State for Health, Osagie Ehanire, said the government was working hard to prevent the resurgence of Lassa fever by developing a Lassa fever research plan, aligned with global research agenda.