Spatiotemporal analysis of within-country imported malaria in Brazilian municipalities, 2004-2022.

Human mobility has challenged malaria elimination efforts and remains difficult to routinely track. In Brazil, administrative records from the Ministry of Health allow monitoring of mobility locally and internationally. Although most imported malaria cases are between municipalities in Brazil, detailed knowledge of patterns of mobility is limited. Here, we address this gap by quantifying and describing patterns of malaria-infected individuals across the Amazon. We used network analysis, spatial clustering, and linear models to quantify and characterize the movement of malaria cases in Brazil between 2004 and 2022. We identified sources and sinks of malaria within and between states. We found that between-state movement of cases has become proportionally more important than within-state, that source clusters persisted longer than sink clusters, that movement of cases into sinks was seasonal while movement out of sources was not, and that importation is an impediment for subnational elimination in many municipalities. We elucidate the vast travel networks of malaria infected individuals that characterize the Amazon region. Uncovering patterns of malaria case mobility is vital for effective microstratification within Brazil. Our results have implications for intervention stratification across Brazil in line with the country's goal of malaria elimination by 2035.

Imported malaria definition and minimum data for surveillance.

The mobility of malaria-infected individuals poses challenges to elimination campaigns by way of spreading parasite drug resistance, straining country-to-country collaboration, and making routine data collection difficult, especially in resource-poor settings. Nevertheless, no concerted effort has been made to develop a common framework to define the spatial and temporal components of an imported malaria case and recommend the minimum data needed to identify it. We conducted a scoping review of imported malaria literature from 2010 to 2020 which showed that definitions vary widely, and local capabilities of detecting importation are often restricted in low-income countries. Following this, we propose a common definition for imported malaria and the minimum data required to identify a case, depending on the country's capability of conducting an epidemiological investigation. Lastly, we utilize the proposed definition using data from Brazil to demonstrate both the feasibility and the importance of tracking imported cases. The case of Brazil highlights the capabilities of regular surveillance systems to monitor importation, but also the need to regularly use these data for informing local responses. Supporting countries to use regularly collected data and adopt a common definition is paramount to tackling the importation of malaria cases and achieving elimination goals set forth by the World Health Organization.

Cross-border malaria in Northern Brazil.

BACKGROUND: Cross-border malaria is a major barrier to elimination efforts. Along the Venezuela-Brazil-Guyana border, intense human mobility fueled primarily by a humanitarian crisis and illegal gold mining activities has increased the occurrence of cross-border cases in Brazil. Roraima, a Brazilian state situated between Venezuela and Guyana, bears the greatest burden. This study analyses the current cross-border malaria epidemiology in Northern Brazil between the years 2007 and 2018. METHODS: De-identified data on reported malaria cases in Brazil were obtained from the Malaria Epidemiological Surveillance Information System for the years 2007 to 2018. Pearson's Chi-Square test of differences was utilized to assess differences between characteristics of cross-border cases originating from Venezuela and Guyana, and between border and transnational cases. A logistic regression model was used to predict imported status of cases. RESULTS: Cross-border cases from Venezuela and Guyana made up the majority of border and transnational cases since 2012, and Roraima remained the largest receiving state for cross-border cases over this period. There were significant differences in the profiles of border and transnational cases originating from Venezuela and Guyana, including type of movement and nationality of patients. Logistic regression results demonstrated Venezuelan and Guyanese nationals, Brazilian miners, males, and individuals of working age had heightened odds of being an imported case. Furthermore, Venezuelan citizens had heightened odds of seeking care in municipalities adjacent Venezuela, rather than transnational municipalities. CONCLUSIONS: Cross-border malaria contributes to the malaria burden at the Venezuela-Guyana-Brazil border. The identification of distinct profiles of case importation provides evidence on the need to strengthen surveillance at border areas, and to deploy tailored strategies that recognize different mobility routes, such as the movement of refuge-seeking individuals and of Brazilians working in mining.