Malaria test positivity among febrile patients at an urban surveillance site in Libreville, Gabon, climbed to 48.1% in 2024, the highest level recorded in a 15-year retrospective analysis of passive surveillance data from the Melen sentinel site. The finding, published in BMC Infectious Diseases, documents a marked resurgence after years of decline, with the proportion of positive thick blood smears falling to a minimum in 2019 before rebounding sharply. Overall, 33,643 patients tested by microscopy between 2010 and 2024 were included, and 35.2% of all slides examined during the period came back positive.
The study, led by Noé Patrick M’Bondoukwé, Denise Patricia Mawili-Mboumba and Marielle Karine Bouyou-Akotet and colleagues, drew on routine records of febrile patients who underwent malaria testing at the Melen site. The team calculated the malaria test positivity rate, or TPR, as the proportion of positive thick blood smears among slides examined, and then related demographic, behavioural and seasonal factors to positivity using logistic models. Estimates were reported as crude and adjusted odds ratios, each accompanied by a 95% confidence interval, allowing the researchers to separate the independent contribution of each factor from the influence of the others.
The trajectory over the study period was not uniform. After an initial increase between 2010 and 2012, positivity declined steadily to its lowest point in 2019. That downward phase then reversed: by 2024 the TPR had reached 48.1%, meaning nearly one in two febrile patients tested at the site had a positive thick blood smear. The authors describe malaria transmission as remaining sustained in urban Libreville, with the recent resurgence signalling that control measures have not held the parasite in check.
Age emerged as one of the strongest correlates of infection. Adults aged more than 15 years showed the highest odds of malaria positivity compared with children under 5 years, while there was no difference in transmission between adults and the 5-to-15-year-old group. The authors interpret this pattern as a shift in the age distribution of malaria positivity towards older age groups, a change they argue has direct consequences for how urban control programmes should target their interventions.
Behavioural factors also left a measurable imprint on the data. Use of an Insecticide-Treated Net was associated with lower malaria test positivity, consistent with the protective role these bed nets play against mosquito bites. Conversely, absence of self-medication and longer fever duration were each associated with increased odds of infection. The link between longer fever duration and higher positivity may reflect the natural course of untreated infection, in which patients who delay care or lack prior drug exposure remain parasitaemic for longer, although the observational design of the study means these associations describe patterns in who tests positive rather than proven causal effects.
Seasonality pointed in an unexpected direction. Malaria test positivity was significantly higher during dry seasons than during rainy seasons at this urban site. In many malaria-endemic settings, transmission peaks during or after the rains, when breeding sites abound; the Libreville pattern suggests that in this urban environment, other dynamics, such as water storage practices, drainage characteristics or the ecology of local vector populations, may sustain transmission even when rainfall is low. The authors highlight the association between TPR and climatic factors as evidence that control strategies need to be climate-informed rather than assuming a single predictable transmission calendar.
The setting matters for how these results should be read. Melen is a sentinel surveillance site, and the data come from passive surveillance: patients who arrived at the facility with fever and were tested by microscopy. This means the TPR reflects the burden among febrile care-seekers at one urban site, not a random sample of the whole city population, and asymptomatic infections circulating in the community are not captured. Sentinel data of this kind are nonetheless valuable precisely because they are collected consistently over long periods, which is what allowed the authors to trace a 15-year trend in a setting where such longitudinal urban records are scarce.
The study’s background notes that malaria remains a major public health problem in sub-Saharan Africa, including Gabon, where urban transmission is increasingly recognised. Despite the strategic importance of sentinel surveillance systems, long-term data describing malaria trends and the factors associated with malaria positivity in urban settings have remained rare. By quantifying how positivity evolved and which patient-level and seasonal factors were related to it, the analysis fills a documented gap in the evidence base for urban malaria control.
The authors conclude that the observed shift towards older age groups, together with the associations between test positivity and behavioural and climatic factors, highlights the need for adaptive, urban-specific and climate-informed control strategies. In practical terms, the data suggest that interventions designed around young children as the principal affected group may need recalibration for a city where adults now show the highest odds of testing positive, and that net promotion remains a relevant lever given its association with lower positivity. The resurgence to 48.1% in 2024, after the 2019 low point, serves as the study’s central warning: urban malaria in Libreville is not a residual problem but a resurgent one, and the surveillance infrastructure that detected the rebound is the same infrastructure that will be needed to track whether control efforts can reverse it.
Subject of Research: Long-term trends and factors associated with confirmed clinical malaria test positivity at an urban sentinel surveillance site in Libreville, Gabon
Article Title: Trends and factors associated with confirmed clinical malaria in an urban sentinel surveillance site in Melen, Libreville, Gabon: a 15-year retrospective study (2010–2024)
Article References: M’Bondoukwé, N. P., James, L. A. J., Mihindou, C. J., Ndong Ngomo, J. M., Moutombi Ditombi, B. C., Zogo Obiang Ella, D.-D., Agbanrin, A. A., Pongui Ngondza, B., Nzambe Nzambe, E., Nymane, T., Mbang Nguema, O. A., Moussavou Mabicka, D. A., Vaillant, M., Mawili-Mboumba, D. P., & Bouyou-Akotet, M. K. (2026). Trends and factors associated with confirmed clinical malaria in an urban sentinel surveillance site in Melen, Libreville, Gabon: a 15-year retrospective study (2010–2024). BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14616-5
Image Credits: AI Generated
DOI: 10.1186/s12879-026-14616-5
Keywords: malaria, Gabon, Libreville, sentinel surveillance, test positivity rate, urban transmission, insecticide-treated nets, thick blood smear, seasonality, retrospective study, febrile patients, public health
News Source: Phoebe Ingram. (October 30, 2026). Urban malaria surges in Libreville as test positivity hits 48.1% in 2024. Scienmag.
