Tackling the Lassa Fever Epidemic

08 Mar 2012

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Multimammete rats

43 years after the first case of Lassa fever was recorded, the country is still grappling with the virus that is transmitted by hairless tailed bush rats that abound in the country. With more than 40 lives already lost and over 400 others infected this year alone, Olaolu Olusina examines the inadequate surveillance system and lacklustre response to the killer virus which is responsible for some 5,000 deaths every year

Nigerians were indeed jolted when the news of a fresh outbreak of Lassa fever was broken by the Federal Ministry of Health about seven weeks ago. Many were further worried at the revelation that the disease, which had spread into 12 states including Edo, Taraba, Borno, Gombe, Yobe, Plateau, Nassarawa, Ebonyi, Ondo, Rivers, Anambra and Lagos States, was being transmitted through a species of bush rats.

At the last count, the government disclosed that hospital records showed that over 40 lives had been lost to the disease which had assumed epidemic proportions with over 400 persons already infected. Edo and Taraba topped the list of states with the highest casualty figures while about 50 million Nigerians are believed to be at risk from the disease which is even killing doctors and nurses.

Rapid Response Committee

The federal government officially responded to the outbreak of the disease on February 22, six weeks after it had wreaked havoc in more than 12 states with the inauguration of a 23-member Rapid Response Committee chaired by Professor Sunday Omilabu, a professor of Virology and Dean, Faculty of Basic Medical Sciences, College of Medicine, University of Lagos.

Charged with the task of preventing and controlling a further outbreak and spread of the virus, the committee, which also has Dr. Henry Akpan of the Federal Ministry of Health as secretary, is expected to submit its full report and recommendations by June.

Inaugurating the committee in Abuja, Minister of State for Health, Dr. Muhammad Ali Pate, said the aim of the committee was to coordinate federal and state governments as well as development partners’ response in controlling further spread of the virus.

He disclosed that the federal government was concerned with the spread of Lassa fever in Nigeria, saying the government had earlier initiated a National Lassa Fever stakeholder’s forum in 2007 to advocate for action against the virus.

“Government would continue to support the treatment of all reported Lassa fever cases with prompt preposition of ribavirin drugs and personal protective equipment. This year, 500,000 vials of the ribavirin drugs were procured and distributed to the affected states,” he said.

The minister also restated the resolve of the federal government to do everything possible not only to control the Lassa fever epidemic but to put in place a mechanism for its effective prevention.

He said the committee will provide technical expertise towards curtailing the outbreak, come up with standard treatment protocols and guidelines for the management of Lassa fever, develop standard operating procedures on infection control in hospitals and mobilise resources for the prevention and control of the disease.

The committee, according to him, will also coordinate intervention activities for the prevention and control of the virus.

“It is expected that this committee will come up with a sustainable framework for combating the scourge of Lassa fever to prevent the loss of lives of the general public and those of the health workers,” Pate added.\

Mixed Reactions

Mixed reactions have, however, trailed the recent outbreak of Lassa fever in the country, just as experts and stakeholders continue to blame the recent outbreak on inadequate surveillance system and monitoring, wondering if this attitude was due to the fact that a prominent person had not died from the disease.

Reacting to the recent outbreak and the inauguration of the Rapid Response Committee in his response to an interview questionnaire from THISDAY, a professor of Virology and the pioneer Vice Chancellor, Redeemer’s University, Ogun State, Professor Oyewale Tomori, said the issue of sudden occurrence of an endemic disease does not arise, where a sensitive surveillance system is in place.

He explained that Nigeria will continue to be taken unawares until the country gets its surveillance and laboratory support systems in order.

“Only then can we detect, predict and foresee these outbreaks and nip them in the bud. May be we could not have prevented all the 40 deaths, but we certainly could have reduced the number to single digits, and it is scandalous that in 2012, 43 years after Lassa fever was first discovered in Nigeria, doctors, nurses and health workers are still dying,” he said.

The Origin

Tracing the origin of the acute viral disease, Tomori said the disease was first discovered in 1969 when two missionary nurses working in Lassa, a town in Borno State, died.

“The cause of their illness was later found to be a virus that was named after the town where the first reported cases occurred,” Tomori explained.

He disclosed further that the virus belongs to a family of viruses, known as the Arenaviridae, a family of some 30 member viruses, found in different parts of the world.

“They cause a variety of diseases ranging from aseptic meningitis and haemorrhagic fever syndromes,” he said, noting “Apart from Nigeria, Lassa fever is known to be endemic in other West African countries, including Guinea, Liberia and Sierra Leone.”


According to Tomori, “The symptoms of Lassa fever are initially varied and non-specific. In about 80 per cent of people infected with the Lassa fever virus, the disease is mild or with no observable symptoms. The remaining 20 per cent have a severe multisystem disease.

Between 1-3 weeks after the patient comes into contact with the virus, the signs and symptoms of Lassa fever typically begin.

These include fever, pain behind the chest wall, sore throat, back pain, cough, abdominal pain, vomiting, diarrhea, conjunctivitis, facial swelling, proteinuria (protein in the urine), and mucosal bleeding.

In some patients neurological problems, including hearing loss which may be transient or permanent, tremors, and encephalitis, have been described.

Tomori, however, noted that the wide variation and the non-specific nature of Lassa fever make clinical diagnosis very difficult.

“The disease may be confused with other febrile diseases such as malaria, typhoid, diphtheria, and other viral hemorrhagic fever diseases such as yellow fever,” he noted.

“Therefore it is imperative and essential that presumptive clinical Lassa fever diagnosis is backed up with specific laboratory diagnosis.”

He nonetheless advised that “early and rapid laboratory confirmation of Lassa fever will ensure the commencement of appropriate treatment and institution of barrier nursing to prevent its spread to especially non-Lassa fever patients on admission and hospital workers including doctors and nurses.”

Dangerous Virus

Just as many Nigerians keep wondering how a disease could kill both the infected as well as the care-givers such as doctors and nurses, Tomori explained that the Lassa virus had been known to be highly dangerous and stubborn, thus necessitating the need for specially equipped laboratories for its diagnosis and confirmation.

“It is most often diagnosed using the ELISA test, that is, the enzyme-linked immunosorbent serologic assays. This detects two types of antibodies (IgM and IgG) as well as Lassa antigen, within hours of receiving an appropriate specimen from a Lassa fever patient. The virus can be grown in the laboratory, but this takes 7 to 10 days in specially equipped laboratories,” he explained.

According to the Professor of Virology, “Diagnosis after the death of a patient can be done using the immune-histochemistry performed on tissue specimens. Other techniques for Lassa virus detection, but more often used as research tools include the reverse transcription-polymerase chain reaction (RT-PCR).

It must, however, be pointed out that definitive confirmation of the disease, must consider both laboratory results and clinical signs and symptoms.”

Seasonal Occurrence?

Fears are now being expressed that the Lassa fever epidemic in Nigeria has become seasonal and experts seemed to have explanations for this, though they are of the view that early surveillance could nip its devastating effects in the bud.

“There appears to be a seasonal clustering between the late rainy and early dry season, although a more sensitive surveillance system may indicate the occurrence of the disease throughout the year with increased number of cases during the dry season,” Tomori explained as he noted that “This may result from the characteristics of the natural host the Mastomys rodent, which is a peridomestic animal.”

According to the professor, “Several factors may be responsible for this apparent seasonal distribution of Lassa fever cases. During the rainy season, it is usually found in the farms and fields around the homes. With the dry season and reduction in types and quantity of food for the rodents, combined with the tradition of storing grains in silos built close the houses, the rodents are found mainly in homes. Add to that the burning of farms during the dry season drives some of the Mastomys to the houses to escape the fires. All these lead to increased exposure to wild rodents.”

Mode of Transmission

It is worthy to note that since the recent outbreak of the Lassa fever epidemic in the country some eight weeks ago, curious Nigerians have been asking how the disease can be contracted given its deadly and dangerous nature.

The curiosity arose from the fact that rats and rodents are everywhere in the country. From the ghettos of Ajegunle and Makoko to the high-brow Victoria Garden City and Ikoyi, there is hardly any place is free of rodents.
Tomori, however, provided an explanation for this concern. “The natural host of Lassa virus - the mastomys  rodent - often lives in and around homes and scavenges on human food remains or poorly stored food. In the process, they shed the virus in urine and droppings on the floor and food. Therefore, a person may be subsequently infected with Lassa virus when he or she is exposed through direct contact, either by touching objects or eating food contaminated with urine or droppings of the rodent host.

“Another way of exposure is through cuts or sores exposed to the rodent droppings. Contact with the virus also may occur when a person inhales tiny particles in the air contaminated with rodent excretions. This is called aerosol or airborne transmission. Where mastomys rodents are killed, roasted and consumed, Lassa virus infection may occur via direct contact when the rodents are caught and prepared for food.

“Lassa fever may spread through person-to-person contact too. This type of transmission occurs when a person comes into contact with virus in the blood, tissue, secretions, or excretions of an individual infected with the Lassa virus. Such person-to-person transmission in health care settings are seen, where, along with the above-mentioned modes of transmission, the virus also may be spread in contaminated medical equipment, such as reused needles (this is called nosocomial transmission),” he explained.

He added that in some village and traditional settings, “Lassa fever transmission has occurred when contact is made with fluids discharged from dead bodies.” The professor, however, noted that “the virus cannot be spread through casual contact (including skin-to-skin contact without exchange of body fluids),” saying, “Lassa virus is shed for three to nine weeks in the urine, and for three months in the semen of recovered Lassa fever cases.”

Case-fatality Rate

Tomori said the real geographical distribution of Lassa fever may extend into other West African countries, because the natural host of Lassa virus, the multimammate rat, also known as the hairless tailed rat, Mastomysnatalensis spp, is found throughout West Africa.

“In areas where Lassa fever is endemic, that is, where the disease is constantly present, it is a significant cause of morbidity and mortality.

“It is estimated that Lassa fever is responsible for between 100,000 to 300,000 cases, with approximately 5,000 deaths every year. These are crude estimates, as in some areas of Sierra Leone and Liberia, where reliable data are available; 10-16 per cent of people admitted to hospitals have Lassa fever, indicating the serious impact of the disease on the population of those areas.

“Lassa fever has been associated with occasional epidemics, during which the case-fatality rate can reach 50 per cent. Unfortunately, poor standards and state of disease surveillance in Nigeria do not allow us to provide data, with confidence, on the morbidity and mortality of Lassa fever in Nigeria, and the impact of the disease on the Nigerian population. Lassa fever is also associated with occasional epidemics, during which the case-fatality rate can reach 50 per cent,” Tomori explained.

But Tomori was quick to allay the fears of many who believe contracting the disease is a sure death warrant. “It is not quite correct to say that Lassa fever kills quickly. There are other diseases in which death occurs much faster. Approximately 15-20 per cent of patients hospitalised for Lassa fever die from the illness within 7-10 days.

“However, overall only about 1 per cent of infections with Lassa virus results in death. The death rates are particularly high for women in the third trimester of pregnancy, and for fetuses, about 95 per cent of which die in the uterus of infected pregnant mothers,” he explained.

Doctors, Nurses Not Exempted

From the first reported cases 43 years ago to this year’s outbreak, doctors and nurses have not been spared of the devastating effects of the disease. Tomori  said a disease that kills the doctors and the nurses charged with treating patients, leading to the closure of the hospitals, will certainly acquire some notoriety, as Lassa fever does.

“In a study of a Nigerian Lassa fever epidemic in 1989, of 34 patients with Lassa fever, including 20 patients, six nurses, two surgeons, one physician, and the son of a patient, there were 22 deaths (65 per cent fatality rate). I was there in 1989†when health workers died in Ekpoma, Enugu, Aba, and Ezinihite in Aboh-Mbaise LGA in Imo State. I was also there in 1993, when doctors and nurses died in Lafia. I am aware of the death of three nurses, one of them pregnant and a doctor who died in Abakaliki in 2008.

“In 2012, we know that, so far, two doctors and four nurses have died of Lassa fever. This is 43 years after the first nurses and doctors died from Lassa fever in Lassa and Jos. Most patients were exposed in the two hospitals where the epidemic occurred. Both outbreak hospitals were inadequately equipped and staffed, with poor medical practice. Compelling, indirect evidence revealed that drug injections were given by minimally educated and poorly supervised staff using the same syringes among patients, who subsequently became infected with the Lassa virus.

“Hospital staff members were not left out as they became infected during emergency surgery and while caring for the Lassa virus infected patients. The hospital was eventually closed. This illustrates the high price exacted when parenteral injections and surgery are carried out without due attention to good medical practice,” he explained.

According to the professor, “It has been 22 years now, when this situation was reported, proper and scientific investigation of the 2011 Lassa fever outbreaks killing doctors and nurses may have resulted from lack of attention to good medical practice.”

Not Learning from Experience

Stakeholders and experts believe that the country has not learnt from experience and the government should have put in place a good surveillance system.

“I believe Lassa fever outbreaks occur regularly in Nigeria and our level of awareness and concern determine how soon we recognize and respond to the outbreaks. We do not yet know where the index case of the current outbreak occurred. We are having this outbreak this time, because we have refused to learn from our 43 years of experience with Lassa fever outbreaks in Nigeria,” Tomori lamented.

He, however, commended the federal government for setting up the Rapid Response Committee.

“This is a step in the right direction. However, coming six weeks after the suspected index case, this cannot be called a Rapid Response Committee. Nigeria cannot and should not depend on establishing ad hoc/emergency rapid response committees each time we have an outbreak of a disease. By now Nigeria should have not only a standing rapid response committee in each of the 36 states of Nigeria, but also a national standing rapid response committee, charged with coordinating the activities at national and state levels. The state committees will assist the rapid response committees in each of the LGAs,” he said.

According to the professor, “The Minister of Health at a press conference narrated the case of a 28-year old female corps member who completed her three weeks orientation in Rivers State, but travelled home to visit her family in Afikpo and Abakalilki, capital of Ebonyi State, where she contracted the fever on January 1 and died two days later .

“Given Lassa fever incubation period of 6-21 days, it is not likely that this was a Lassa fever case or she contracted the disease much earlier in River State. Was this the index case, and the beginning of the spread to the other states of Edo, Nasarawa, Plateau, Taraba, Yobe, Ondo, Anambra, Delta and Lagos?

“It is possible that some of the cases were ‘importations’ from other states. However, that it took six weeks, assuming the case narrated by the minister was the first case, it says much about the poor state of our diseases surveillance, detection and response. This unacceptable state of disease surveillance may have been responsible for the spread to so many states and the deaths of doctors and nurses and other health workers.

“A situation where the healer succumbs to the disease he is supposed to heal, calls for an urgent need to improve our disease surveillance and take a new look at our training we provide in our medical and health institutions. We certainly cannot give the excuse that Lassa fever is a rare disease in Nigeria. No year has passed since 1969, when Lassa fever was discovered, that we have not had epidemics of varying proportions in Nigeria.

“If 43 years after the discovery of Lassa fever, it still takes us six weeks to officially alert the public and respond, then we certainly have a very long way to go. If we do not change our attitude, the 2013 Lassa fever epidemic will take a much longer time to detect and institute appropriate response.”

Inadequate Laboratories

THISDAY reliably learnt that only two laboratories in the country have the capacity to screen blood for Lassa fever and these are the Irrua Specialist Hospital in Irrua, Edo State and the Central Medical Laboratory at the Lagos University Teaching Hospital (LUTH), though the Minister of Health said there are nine specialist centres across Nigeria where tests on Lassa fever can be done.

But Tomori said much still has to be done. “The question we need to ask is how many of these nine centres are functional? How many of them have reagents to test samples? The last information I had was that nearly all the samples were being tested in one centre at Irrua. The Irrua centre is functional, perhaps not because of what we have done to make the place operational. It is a place highly and, to a considerable extent, supported by funds from an organisation outside Nigeria,” he volunteered.

He also stressed the need to intensify programmes for rodent control and avoidance in the rural areas and urban slums.
“Specifically, we must educate our people to properly store food in rodent-proof containers, clean their surroundings and make the areas unfriendly for rodents to inhabit. When we find rodents, they must be killed and their carcasses properly and safely disposed. As much as possible we must avoid rodents as a food source,” he advised.

Sensitisation and Action

THISDAY, however, learnt that awareness and sensitisation on the disease have increased in the past two weeks with state and local governments leading the vanguard by sensitising their people on the need to keep a clean environment.

Chairman of the Rapid Response Committee, Professor Omilabu, told THISDAY last week that his committee, which has up till June to submit its report and make recommendations to the federal government, will sustain the increased tempo of awareness and action on the disease.

He said aside the two functional laboratories; the federal government was in the process of strengthening seven other laboratories across the geo-political zones to tackle the disease.

“Presently we can handle the situation. The federal government has put in place drugs, personal protective equipment for doctors and nurses, as well as increased the health education effort. Blood samples are being sent by courier. There is a WHO criterion for sending samples. We are treating all the states as the same as even a single case is regarded as an epidemic. Efforts are on-going to get a very potent vaccine. The virus is not stable, it changes fast. We want to find out which of the proteins of the virus will make the vaccine work. But the drug - ribavirin - is quite efficacious if detection is made very early.

“We have up till June to submit our report and recommendations to the federal government. Under the terms of reference of our assignment, we are to work on the technical aspect of the disease - strengthen the laboratories and the capacity of the doctors to enable them handle patients without exposing themselves to the virus. We are also to procure more drugs to ensure that those infected get adequate dose of the drugs.

“We are also expected to draw up a master plan with respect to mobilising the states and federal government to support the health education aspects of Lassa fever. We are also to put in place a surveillance structure to move beyond the 12 states. We are expected to draw a blue-print to assist the government tackle the epidemic,” Omilabu told this reporter.

Assuring that the federal government had procured enough quantities of the drugs for the disease, he said, “There is no cause for alarm. We know the virus and how it is transmitted. We know the prevalence is high during the dry season. We should increase alertness and people should maintain good health and protect their food from rodents.”

Tomori also commended the renewed effort. “Now that the government has swung into action, we only hope the action will be sustained. The newspapers and the media testify to the action of government, and the government should be commended, at least for finally taking action.

“I think I can say now that the government has swung into action, we are likely to see the epidemic controlled. They even provided contact telephone numbers to call in case of emergencies. If these epidemics are caused by ‘new’ agents, one may excuse the performance of the government. Now is the time for the government to put in place permanent structures to help minimise the devastation caused by endemic diseases, so we do not have a repeat of the current situation,” he said.

A Poor Man’s Disease

But many people, including Tomori, are of the view that the government may not really take the issue seriously until a big man dies of the disease.

“I remember during the military era, a doctor told the military governor of one of the states that the governor may have contracted Lassa fever. An air force plane was dispatched to the Ibadan aerodrome to pick my boss and me to come to the state capital to collect a blood sample from the governor. The jet was on standby to return us to Ibadan to test the sample. In the plane were two other officers, one was totting a vicious looking gun.

“In 1993, during the Lafia Lassa fever epidemic, I was asked a question. What do you think can happen in Nigeria to make the country take Lassa fever seriously? Without batting an eyelid, I said ‘Not until a big man, a Director General in the ministry, a minister, an honourable member of one of parliament, a prominent oba/eze/emir, a governor, or perhaps the vice president or even the president - dies of Lassa fever, before we will take the issue seriously. I have not seen anything yet, to make me change that answer,” Tomori stated.

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