Mapping of the country-wide prevalence of non-malarial febrile illnesses in areas with varying malaria transmission intensities in Mainland Tanzania

Background Despite the declining malaria burden in endemic countries, reports of febrile episodes do not align with the current patterns of malaria transmission. This highlights the presence of non-malarial febrile illnesses (NMFIs), which are difficult to distinguish from malaria. This study assessed the country-wide prevalence of NMFIs and their patterns across various malaria transmission settings in Mainland Tanzania. Methods A cross-sectional study recruited patients aged ≥ 6 months from 86 health facilities in all 26 regions of Tanzania. All patients were tested for malaria using rapid diagnostic tests (RDTs). For this study, patients with fever who tested negative by RDT were operationally classified as having NMFIs and their prevalence was determined accordingly, Logistic regression was used to determine factors associated with NMFIs. Results Of the 18,568 patients tested, 8,273 (44.6%) were considered to have NMFIs because they tested negative by RDT. Higher prevalence of NMFIs occurred in females (45.8%) than in males (42.8%), adults (aged ≥ 15 years, with 50.6%) compared to under-fives (42.6%) and school children (aged 5 -< 15 years, 34.3%), and in very low (65.5%) compared to high transmission areas (34.5%). NMFIs were significantly more likely in females than in males (aOR = 1.18, 95% CI = 1.10–1.26), under-fives (aOR = 1.60, 95% CI = 1.47–1.76) and less likely in high transmission areas (aOR = 0.11, 95% CI = 0.08–0.13), and school children (aOR = 0.70, 95% CI = 0.64–0.77). Conclusion The findings show a high prevalence of NMFIs overall, and higher prevalence and odds of NMFIs in females and individuals from low and very low transmission areas. These groups should be targeted with appropriate point-of-care tests and treatment strategies.