Burden of Malaria in Adults in Sahelian Niger: A Retrospective Study (2019-2021).

In the Sahel, malaria transmission is highly dependent on rainfall, and control efforts are conducted during the rainy season. However, because of climate changes, the objectives of this study were to better define the period of transmission in the different ecoclimatic regions and the burden of the disease in young adults, which is poorly investigated. The data from districts in the different ecological zones of Niger were compared. During this study, 26% of all consultations were malaria related, of which 59% were malaria confirmed. This represented 12,000 to 19,000 cases and 12.9 to 25.6 deaths per 100,000 inhabitants. An increase of incidence was seen over the study period but a decline in case fatality rate was also observed. Depending on region, children under 14 years of age (half of the population) accounted for 43-80% of cases, which in contrast, underlines a significant malaria burden in young adults, especially in arid regions where transmission is lower. The majority of cases occurred from August to October but appeared later in arid zones. The number of cases positively correlated with the cumulative rainfall over the previous five weeks. However, 17-26% of cases were identified during the dry season. This study highlights a high transmission rate that extends throughout the dry season, with ∼50% of cases registered representing patients >14 years of age, and 25% of cases >25 years. Young adults should thus be considered an at-risk group and should be included in strategies for control.