Mobility and malaria incidence in Indonesia's low-endemic areas during the COVID-19 period.

backgroundHuman mobility significantly impacts the transmission and persistence of malaria, even in low-endemic areas. The COVID-19 pandemic caused significant shifts in mobility patterns across Indonesia. This study examines the association between population mobility and malaria incidence in low-endemic Indonesian districts during the COVID-19 period.

methodsThe study was conducted from March 2020 to May 2022 in four districts, i.e., Kulon Progo and Purworejo (Java Island) and Tanah Laut and Tanah Bumbu (outside Java Island). Data were collected from district health office reports on COVID-19 cases, mobility data from Facebook, malaria testing, and case reports from the district health office's electronic system. Multivariable Poisson regression was used to examine the association between mobility and malaria incidence, adjusting for district location, endemicity of mobility origin, malaria testing intensity, and COVID-19 burden.

resultsA total of 480,575 mobility events were examined, showing that mobility peaked in 2021 outside Java Island, with Tanah Bumbu exhibiting the highest mobility rate (36.6%). In Java, most mobility came from elimination areas (> 80%), while outside Java areas showed mobility from the low-endemic regions (48.5% and 87.9%). In Purworejo, mobility fluctuated in 2020, with peaks in March and May 2021, correlating with a rise in malaria cases. In Kulon Progo, mobility increased only slightly, but malaria cases spiked in late 2021 and early 2022. No clear pattern was found between mobility and malaria cases in Tanah Bumbu and Tanah Laut. Malaria examination rates dropped significantly during the early months of the pandemic. The incidence of malaria outside Java was 64% lower than in Java, and increased mobility was associated with higher malaria incidence. In the pooled multivariable Poisson regression, mobility, malaria screening, and COVID-19 positivity were associated with malaria incidence [IRR 1.25 (95% CI 1.21-1.30), IRR 2.33 (95% CI 2.22-2.45), and IRR 1.12 (95% CI 1.08-1.17), respectively]. However, descriptive analysis showed no clear temporal association between mobility trends and malaria cases outside Java, suggesting the relationship is context dependent.

conclusionsMobility remains a crucial factor in malaria control, although its relationship is complex and context-dependent, influenced by local patterns of endemicity. These findings are associated in nature and do not causal effects. Targeted interventions during such periods are essential to prevent a resurgence of the disease. Specifically, the National Malaria Control Program should consider integrating real-time digital mobility indicators into SISMAL to generate mobility-informed risk alerts for districts experiencing elevated inflows from endemic areas.