Malaria prevalence and epidemiological characteristics in Northern Malawi: a nine-year retrospective hospital-based study

Abstract

BACKGROUND: Malaria remains a major public health challenge in Malawi, yet contemporary epidemiological data from northern Malawi are limited. This study aimed to characterize the prevalence, demographic distribution, temporal patterns, and parasite density of malaria using routine laboratory surveillance data from a tertiary referral hospital. METHODS: test or Fisher's exact test, with Bonferroni correction for multiple comparisons. Parasite density, available for a subset of confirmed cases from 2024-2025, was summarized as median (interquartile range [IQR]) and compared using the Mann-Whitney U test or Kruskal-Wallis test. RESULTS: A total of 31,253 individuals were screened, of whom 3405 were laboratory-confirmed malaria cases, yielding an overall prevalence of 10.89%. Plasmodium falciparum accounted for 86.23% of identified infections. Malaria prevalence was significantly higher among males than females (11.85% vs. 10.01%, P < 0.001). Children aged < 5 years (13.11%) and 5-14 years (13.31%) had significantly higher prevalence than adults (P < 0.001). Annual malaria prevalence ranged from 7.99 to 12.81% during 2018-2024. Clear seasonal variation was observed, with prevalence consistently peaking during the second quarter (April-June) and declining during the third quarter (July-September). Parasite density decreased significantly with age (p < 0.001), with children aged 5-14 years showing the highest median density (6,285 parasites/μL), but did not differ by gender or season. CONCLUSIONS: Malaria remains highly endemic in northern Malawi, with substantial age- and season-related heterogeneity in transmission. Children younger than 15 years experienced both the highest malaria prevalence and parasite densities, while transmission increased during and immediately after the rainy season. These findings provide updated region‑specific evidence to support targeted, age‑ and season‑tailored malaria control strategies, and highlight the need for strengthened surveillance and preventive interventions in high‑risk populations.