… warns of resurgence if ITN coverage is not sustained
The Nigerian Institute of Medical Research (NIMR) has reinforced its leadership in data-driven public health research as one of its scientists, Ms. Wakila Tijani, unveiled a comprehensive malaria transmission model highlighting the risk of resurgence in high-burden states if insecticide-treated net (ITN) coverage is not sustained.
The study, conducted under the Nigeria Modelling Fellowship by the Corona Management Systems, in collaboration with the Federal Ministry of Health, Nigeria Centre for Disease Control (NCDC), World Health Organization (WHO), and the Gates Foundation, analysed malaria cases between 2018 and 2024, integrating epidemiological, climatic and intervention data.
Nigeria continues to bear the highest global malaria burden, accounting for approximately 27 per cent of cases and 31 per cent of deaths worldwide, according to the 2022 World Malaria Report.
“Malaria remains one of the most significant public health challenges in Nigeria,” Ms. Tijani explained. “By applying mathematical modelling to local data, we are able to better understand how transmission occurs and how specific interventions can significantly reduce infection levels.”
Focusing on a high-prevalence state, Imo, with malaria prevalence of 26.2 per cent, Ms. Tijani’s study examined confirmed malaria cases, rainfall patterns, temperature variations, and ITN ownership and usage trends.
The findings show that malaria cases declined sharply between 2018 and 2021 following the 2017 mass distribution of insecticide-treated nets. However, a gradual increase in cases was observed from late 2022 through 2024.
According to the researcher, declining coverage and behavioural adherence could weaken malaria control gains.
“Our findings suggest that the benefits of net distribution campaigns can diminish over time if coverage and usage are not sustained,” she noted. “Regular replacement of nets and continued public awareness are essential to maintaining protection.”
According to Ms. Tijani, this decline in coverage and usage may be contributing to renewed transmission risks.
“While intervention efforts initially reduced malaria transmission, sustaining high coverage and effective usage remains critical to preventing resurgence,” she noted.
Rainfall Identified as Major Seasonal Driver
The research also revealed a strong seasonal pattern in malaria transmission. Time-series analysis showed that malaria cases typically increased shortly after rainfall peaks, reflecting the impact of rainfall on mosquito breeding and parasite transmission.
Temperature showed some influence but had a less consistent direct relationship with malaria case spikes.
“Rainfall emerged as a key seasonal driver of malaria transmission in the study area,” the researcher said. “This highlights the need to align malaria interventions with seasonal transmission patterns.”
Ms. Tijani developed a deterministic malaria transmission model incorporating both human and mosquito populations. When intervention measures such as insecticide-treated nets were included in the model, the simulations showed:
- A steady decline in infected human populations
- Gradual reduction in infected mosquito populations
- Stabilisation of malaria transmission over time
However, when intervention parameters were removed, infections remained persistently high.
Further simulations revealed that increasing ITN effectiveness and usage to about 80–90 per cent could significantly reduce malaria transmission, in line with World Health Organization recommendations.
The study estimated the Basic Reproduction Number (R₀) at 2.40 in the absence of intervention, indicating strong transmission potential.
Under ITN intervention, the Effective Reproduction Number fell to 1.10 — an improvement but still above the threshold required to halt sustained transmission.
Sensitivity analysis identified mosquito biting rate, ITN usage, and ITN effectiveness as the most influential drivers of malaria transmission.
The study provides strong evidence for:
- Scaling up ITN coverage to at least 80 per cent
- Strengthening sustained community usage
- Integrating rainfall-driven seasonal targeting into malaria control planning
- Expanding subnational modelling to guide interventions.
Also, the study demonstrates the value of localised mathematical modelling in guiding malaria control efforts and supporting national elimination goals.
Commenting on the implications of the findings, the Director-General of NIMR, Professor John Oladapo Obafunwa, emphasised the importance of evidence-based strategy in malaria control.
“Nigeria cannot eliminate malaria with assumptions — we must eliminate it with evidence. This modelling study from NIMR demonstrates clearly that sustained intervention coverage, particularly with insecticide-treated nets, is not optional but essential.
“At NIMR, we are strengthening Nigeria’s capacity to generate the data, models and predictive tools required for precision public health. Our commitment is to ensure that national and subnational malaria control strategies are guided by rigorous scientific evidence. With sustained political will, adequate coverage, and climate-informed planning, malaria elimination in Nigeria is achievable.”
Through initiatives such as the Nigeria Modelling Fellowship Programme, NIMR continues to build indigenous capacity in advanced epidemiological modelling, contributing evidence-based insights to national and global malaria elimination efforts.