Patterns and determinants of imported malaria near Argentina-Bolivia border 1977 - 2010

Abstract

In the Americas, the number of malaria cases has decreased dramatically in the past 15 years, and malaria elimination is now in sight for many countries. Argentina is currently free of autochthonous malaria transmission. Until 2011, cases of malaria were concentrated in the Northwest near the border with Bolivia, a country that continues to have malaria transmission. Orán department, in Salta province, had particularly high transmission near a main road that is a pathway for migration from Bolivia. The purpose of this research was to identify which factors best explain the extent and timing of changes in the proportion of malaria cases in this area that were locally transmitted versus acquired in another country. Combining information from routinely collected case investigations, epidemiological surveillance data, and satellite imagery, we used a logistic model and a multilevel model of change to identify how demographic and place-level variables influence the proportion of malaria cases that were imported over time. The findings showed that the proportion of cases that were imported varied significantly over time and that the variation could be explained by the demographic characteristics of cases. In particular, there was a change in transmission patterns after a cross-border intervention was launched in 1996. In addition, proximity to mosquitos was an important determinant of local transmission. Based on lessons learned from the characterization of transmission trends, policies were proposed for preventing malaria reintroduction in Argentina.