Human mobility complicates malaria elimination efforts in Bangladesh: Study

Human mobility is posing a major challenge to Bangladesh's malaria elimination efforts, as the frequent movement of people between endemic and non-endemic regions helps spread the parasite across the country, according to a new study published in Nature.

The research, which focused on malaria transmission in the Chittagong Hill Tracts (CHT), found that population movement facilitates the mixing and importation of parasites between districts with varying transmission rates. The study suggests that malaria elimination strategies must account for how people travel between areas and the relative importance of local transmission versus parasite importation.

"Frequent travel between endemic and non-endemic regions, along with asymptomatic carriers of malaria, makes it challenging to fully prevent the reintroduction and re-establishment of malaria parasites into regions with no local infections," the researchers said.

To better understand this dynamic, the team built a mathematical model combining human movement data with malaria incidence records across the CHT. Their findings indicate that elimination works best when control efforts target both areas with high malaria transmission and those that are well connected to more populated districts.

"Focusing only on areas with high numbers of cases is not enough to achieve elimination," the study noted, adding that understanding "source" and "sink" regions - areas that export or import malaria parasites - is key to effective intervention.

The study also highlights that previous efforts relying solely on local incidence rates could be misleading, as patients are often diagnosed in places different from where they were infected.

To model population mobility, researchers used mobile phone call detail records (CDRs) to trace movement patterns. However, due to sparse mobile network coverage in forest and fringe areas, where malaria vectors are common—they developed a gravity model to infer movement in less-connected regions.

The model revealed that the highest malaria transmission occurred along the forested border regions in the southeast CHT. However, the greatest reduction in overall incidence could be achieved by prioritising interventions in areas with both high transmission and strong links to western, more populated districts.

"Our results show that the greatest impact in reducing overall incidence through local interventions are in places with both high transmission intensity and high connectivity," the study said.

The researchers concluded that their framework can help public health officials in Bangladesh allocate resources more effectively, particularly in regions with diverse transmission levels and strong inter-district mobility.