Nigeria accounts for over 50% of West Africa’s 2.7 million annual Lassa fever cases -Report 

Nigeria is at the forefront of the Lassa fever crisis in West Africa, with a recent study revealing that the country bears over 50% of the West Africa’s cases of 2.7 million.

The comprehensive research, conducted by the Nigeria Centre for Disease Control (NCDC) in collaboration with Oxford and Liverpool Universities and the Liverpool School of Tropical Medicine, and published in Nature Medicine, highlights the severity of the situation in Nigeria.

The report predicts that, without vaccination, Nigeria would account for about 52.9% of all Lassa virus infections annually. Most of these infections are due to zoonotic spillover from animals, rather than from person-to-person transmission, because the virus spreads less easily between people.

Key findings of the study 

This staggering figure underscores the critical burden that Lassa fever places on Nigeria’s healthcare system.

Nasarawa State, in particular, is highlighted as having the highest annual incidence of Lassa fever in Nigeria, with an estimated 978 infections per 100,000 people. This makes it one of the most severely affected regions in the country.

Vaccination impact 

It indicates that if a vaccine with 70% efficacy against Lassa fever disease were implemented, it could potentially prevent about 10.5% of disability-adjusted life years (DALYs) in Nigeria. DALYs are a measure that combines years of life lost due to premature death and years lived with disability, reflecting the overall impact of the disease on public health.

Moreover, the study highlights that if a more effective vaccine, with 90% efficacy against both the infection and the disease, were introduced, the potential reduction in DALYs could rise to 15.3%.

This means that a more effective vaccine could have a significantly greater impact on reducing the disease burden by preventing a larger proportion of both severe cases and deaths, ultimately leading to a healthier population with fewer life years lost to the disease.

Despite these potential benefits, the effectiveness of vaccination per capita is projected to be higher in other endemic countries such as Guinea, Liberia, and Sierra Leone. This is due to these countries having a higher proportion of their populations in endemic areas compared to Nigeria.

The report notes that about 16% of Nigeria’s total population could be vaccinated over a 10-year period under the current scenarios.

Emergence of lassa-X 

The study also addresses the potential threat of a new strain of the Lassa virus called Lassa-X. According to the model used in the research, this new strain could cause significant and rapid outbreaks across West Africa. The model predicts that Lassa-X could spread to approximately 88.3% of the districts covered in the study.

Nigeria is anticipated to face the highest number of Lassa-X infections compared to other countries, with Niger and Ghana also expected to experience substantial outbreaks. This indicates that Nigeria will likely bear the brunt of the impact from Lassa-X, given its large population and the current burden of Lassa fever.

The report further emphasizes that the projected impact of Lassa-X is surrounded by a high level of uncertainty. This uncertainty arises from the unpredictable and variable nature of how outbreaks might develop and spread. Because Lassa-X is a new strain, the exact patterns of its spread and the scale of its impact are not fully predictable, adding to the challenges of preparing for and managing potential outbreaks.

Implications for public health 

With the country’s substantial share of Lassa fever cases, it is crucial to strengthen efforts to control the spread of the disease and address the challenges posed by emerging strains like Lassa-X.

The research highlights the critical role that vaccination could play in reducing the disease burden, although the per capita benefits may be higher in other endemic countries. The emergence of new strains further complicates the situation, emphasizing the need for continued vigilance and proactive measures in managing Lassa fever in Nigeria.

Overall, the study provides a detailed and pressing call to action for improving public health strategies and expanding vaccination efforts to tackle the ongoing Lassa fever crisis in Nigeria and across West Africa.