Major facts to note about Lassa Fever

Lassa fever
Lassa fever

The death toll from the Lassa fever outbreak ravaging the country since the beginning of the year recently increased to 110, according to the Nigeria Centre for Disease Control (NCDC).

This means the country is currently battling its largest Lassa fever outbreak in history.

From January 1 to March 4, 2018, 1121 suspected cases have been recorded, out of which 353 were confirmed positive, eight probable, 723 negative (not a case) and 37 are awaiting laboratory results (pending).

The rate at which the disease is spreading has become worrisome to the government, health workers and citizens.

Here are six important questions the 2018 Lassa fever outbreak poses and possible answers to them from the Chief Executive Director of the NCDC, Chikwe Ihekweazu.

1      On why three Nigerian states still have the highest prevalence rate despite being equipped with facilities and manpower?

Mr. Ihekweazu said: With the presence of case management and diagnostic capacities in these states, there is an increased focus on surveillance and high index of suspicion for Lassa fever as well as increased awareness among healthcare workers and the public. A person presenting with fever and testing negative for malaria, is more likely to be tested for Lassa fever in the States with this capacity.”

2  On why the predominant age-group affected is 21-40 years?

“This is what we have found – the reason for this will require further research which will happen over the next few weeks as we dig deeper into the factors relating to this outbreak. There are many theories that we are exploring on why this is the case – but the answers will come from the research that we are about to undertake. Previous research done during outbreaks in the past shows that all age groups are affected, with median age being about 32 years, so we have not seen that much change…”

3       On why the male to female ratio for confirmed cases is 2:1?

“Again research activities by the Nigeria Centre for Disease Control in collaboration with the World Health Organisation and other agencies will provide a better understanding of the drivers of this outbreak, including demographic characteristics such as this.”

4         On why health workers are secondary victims to the disease?

“Healthcare workers are responsible for managing infected cases and as such, are exposed to these patients and always at high risk for infection. The risk of transmission of infection from patient to healthcare worker is high when universal care precautions are not implemented. It is therefore important for healthcare workers to wear gloves, appropriate personal protective equipment and ensure infection prevention and control procedures are in place for the management of cases. We are continuously working with healthcare workers to reduce their risk for infection, through the implementation of better infection prevention and control.”

5         On why no confirmed case has been recorded in Borno State where Lassa fever was first reported in 1969?

“There have been suspected cases from Borno during this current outbreak, but none confirmed as Lassa fever. This is a good thing! While this may be due to the changing epidemiological situation where most cases of the disease are being reported from the dense forest areas in Southern Nigeria, we will continue strengthening our disease surveillance activities across all States to ensure all cases are recorded. Despite the insurgency, Borno State is rebuilding its surveillance system and has achieved remarkable progress in this area.”

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6         And finally, on why Nigeria is battling its largest Lassa fever outbreak in 2018?

The reason for the large number of cases this year is the primary subject of ongoing research. We recently published results of a sequencing exercise carried out by the Irrua Specialist Teaching Hospital with support from the Bernard Nocht Institute for Tropical Medicine and other partners. We found that the virus itself has not changed significantly. 

“What we have seen is an improved surveillance system from the local government to national level, increased index of suspicion and awareness among the public as well as the expansion of diagnostic capacity in the country with the addition of the National Reference Laboratory, Abuja. As we continue to strengthen these systems, we will find more cases of the disease. Our response activities remain top priority and we are working very hard to control this outbreak and mitigate potential outbreaks.”

Important facts to note about Lassa fever

  • The illness was first discovered in Nigeria when two missionary nurses succumbed to the virus in 1969. Its name is derived from the village of Lassa in Borno State where it was first documented.
  • The disease is endemic to a number of West African countries. There are estimated to be between 100,000 and 300,000 cases of Lassa fever per year and approximately 5,000 deaths due to the disease.
  • It occurs more in the dry season than in the rainy season.
  • The Lassa virus is caused by a species of rodents called the Natal multimammate rat, the common African rat, or the African soft-furred rat.
  • The most common method of transmission is the consumption or inhalation of rat urine or faeces. Lassa fever can also be spread through cuts and open sores.
  • Symptoms generally appear within 1-3 weeks following infection.
  •  Person-to-person contact is possible via blood, tissue, secretions or excretions, but not through touch. Lassa fever can also be passed between patients and staff at poorly-equipped hospitals where sterilisation and protective clothing is not standard.
  •  In the early stages, Lassa fever is often mis-diagnosed as common cold, typhoid or malaria, and as a result, many patients fail to receive appropriate medical treatment. The onset of the illness is typically mild, with no specific symptoms that would differentiate it from other illnesses.
  • It has an incubation period of six to 21 days after which an acute illness develops.
  • Early signs include: fever, headache and general body weakness, followed by sore throat, nausea, vomiting, abdominal pain and diarrhoea in some cases. After four to seven days, many patients will start to feel better, but a small minority will present with multi-organ involvement.
  • Death from Lassa fever most commonly occurs 10 to 14 days after symptom onset. Non-specific symptoms are facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding.
  • There are three ways by which the virus can be treated and also prevented from further spread. These are implementation of barrier nursing, which is isolation of victims, tracing of people that have come in contact with sufferers as well as the initiation of treatment with the only available drug, Ribavirin. The latter is only effective if administered early, within the first six days after disease onset
  • To avoid contracting the disease, the primary source of transmitting the disease to humans should be prevented.  This can be possible through avoiding contact with rats – particularly in the geographic areas where outbreaks happen. Putting food away in rat-proof containers and keeping your home clean help with ‘discouraging’ rats from entering your home.


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