Travel Is a Key Risk Factor for Malaria Transmission in Pre-Elimination Settings in Sub-Saharan Africa: A Review of the Literature and Meta-Analysis.

Sundus Ahmed,Jeremiah M Ngondi,Richard Reithinger,Stephen K Kaptoge

doi:10.4269/ajtmh.18-0456

Abstract

.By sustaining transmission or causing malaria outbreaks, imported malaria undermines malaria elimination efforts. Few studies have examined the impact of travel on malaria epidemiology. We conducted a literature review and meta-analysis of studies investigating travel as a risk factor for malaria infection in sub-Saharan Africa using PubMed. We identified 22 studies and calculated a random-effects meta-analysis pooled odds ratio (OR) of 3.77 (95% CI: 2.49–5.70), indicating that travel is a significant risk factor for malaria infection. Odds ratios were particularly high in urban locations when travel was to rural areas, to more endemic/high transmission areas, and in young children. Although there was substantial heterogeneity in the magnitude of association across the studies, the pooled estimate and directional consistency support travel as an important risk factor for malaria infection.

Highlights

They primarily reported results from study sites with low transmission intensity, and all used logistic regression modeling to test the association of history of travel with malaria infection status
Most of the studies recruited patients diagnosed with malaria at particular health facilities for inclusion; seven studies surveyed randomly selected households across the study area; one study in Botswana11 looked at all inhabitants of the study site, and one study in Ethiopia19 looked at all current residents of the seven villages selected
The results of the meta-analysis strongly suggest that travel is a key risk factor for acquiring malaria infection, in urban areas and when travel is to rural/malaria-endemic areas or areas of higher transmission intensity than the origin location

Summary

Introduction

It is widely recognized that human mobility influences the spread of infectious diseases, and evidence suggests that human movement was partly responsible for the failure in the previous global malaria eradication campaign. Over the last century, following widespread malaria control/elimination strategies, transmission risk varies markedly between and within countries; travel across different transmission settings markedly influences malaria vulnerability, especially in areas with high malaria receptivity. In the past, malaria and travel largely focused on international travelers to countries or areas at risk of transmission arriving from countries of no risk, who were more susceptible to severe malaria because they lacked immunity. Tremendous progress in the reduction in malaria morbidity and mortality has been achieved in the last decade, with 21 countries projected to attain elimination by the year 2020.5,6 imported malaria has become an important risk factor in formerly malaria-endemic countries that had attained elimination and in low transmission countries that are targeted for elimination. Tremendous progress in the reduction in malaria morbidity and mortality has been achieved in the last decade, with 21 countries projected to attain elimination by the year 2020.5,6 imported malaria has become an important risk factor in formerly malaria-endemic countries that had attained elimination and in low transmission countries that are targeted for elimination. These settings continue to experience thousands of malaria cases every year through importation, resulting in increased morbidity and mortality, a substantial burden to the health system, and occasionally secondary transmission.. These settings continue to experience thousands of malaria cases every year through importation, resulting in increased morbidity and mortality, a substantial burden to the health system, and occasionally secondary transmission. Findings from analyses of international population movements using census-based migration and reported malaria data suggested that certain groups of countries were much more strongly connected by relatively high levels of population and infection movement than others. in malaria post-elimination and preelimination settings, imported malaria remains an important threat to the gains that have been achieved.

Methods

Results

Conclusion