On multifactorial drivers for malaria rebound in Brazil: a spatio-temporal analysis

Background Malaria incidence in Brazil reversed its decreasing trend when cases from recent years, as recent as 2015, exhibited an increase in the Brazilian Amazon basin, the area with highest transmission of Plasmodium vivax and Plasmodium falciparum . In fact, an increase of more than 20% in the years 2016 and 2017 revealed possible vulnerabilities in the national malaria-control program. Methods We studied factors that are potentially associated with this reversal, including migration, economical activities, and deforestation, and weakening of investment in control programs. We analyze past incidences of malaria cases due to Plasmodium vivax and Plasmodium falciparum with a spatio-temporal Bayesian model using more than 5 million individual records of malaria cases from January of 2003 to December of 2018 in the Brazilian Amazon to establish the municipalities with unexpected increases in cases. Results We observe an increase in imported cases from border countries in Roraima state and found small effects due to deforestation and change of occupations. Also, an overall funding reduction from 2013 to 2016 happened before an increase in malaria cases in five regions in Amazon basin, markedly for P. vivax incidence and especially, in Pará and Roraima States. Conclusion Urban developments, discontinued funding for control programs, migration from border areas, deforestation activities, and different economic activities such as mining and agriculture appear linked to the rebound on malaria incidence. These multifactorial drivers show that malaria control programs require permanent attention towards elimination.