Factors associated with hospitalizations due to severe malaria in the non-endemic Brazilian region: a case-control study in the extra-Amazon Region from 2011 to 2019.

BACKGROUND: Malaria is infectious disease with low occurrence in Brazil extra-Amazon Region. Despite this, higher lethality is observed in this region compared to the country's endemic area. Therefore, this study aimed to analyse factors associated with malaria hospitalizations (severe malaria) in the extra-Amazon Region, in order to prevent deaths. METHODS: A case-control design was used, utilizing data from the Brazilian Notifiable Diseases Information System (Sinan) and hospitalization records from the Unified Health System (SIH/SUS) from 2011 to 2019. Cases comprised hospitalized malaria patients, while controls included reported malaria notifications without hospitalization. Probabilistic record linkage techniques were employed, and associations were analysed using multiple logistic regression with a 0.05 significance level. RESULTS: The main risk factors identified were: Black or mixed-race ethnicity (OR = 1.22; 95% CI 1.04-1.43), low education (elementary school OR = 2.21; 95% CI 1.78-2.75 or high school OR = 1.72; 95% CI 1.39-2.13), infection outside the extra-Amazon Region (Amazon Region OR = 1.50; 95% CI 1.15-1.96 or abroad OR = 1.72; 95% CI 1.28-2.32), high parasite count (501 to 10,000/mm3 OR = 1.51; 95% CI 1.27-1.80, 10,001 to 100,000/mm3 OR = 1.77; 95% CI 2.87-1.96 or higher than 100,000/mm3 OR = 3.15; 95% CI 2.20-4.50) and delayed treatment (after 3-7 days symptoms onset OR = 1.74; 95% CI 1.36-2.24 or 8 days or more OR = 2.08; 95% CI 1.62-2.66). Active case detection was a protective factor (OR = 0.65; 95% CI 0.54-0.78). CONCLUSIONS: Delayed treatment remains a key factor in the occurrence of severe malaria, leading to high parasitaemia and revealing inequalities in access to healthcare based on socioeconomic differences. Travel to the Amazon Region or other countries also poses a challenge, requiring strengthened traveller health strategies and increased surveillance awareness to promptly suspect and identify cases.