Risk factors associated with dengue lethality: case-control study, Joinville, Brazil

Dengue remains a major public health concern in Brazil, with approximately 6 million cases and over 6,000 deaths reported in 2024. Joinville, in southern Brazil, recorded one of the highest incidence rates in the country. Understanding the clinical and demographic factors associated with dengue-related mortality in this region is essential for developing effective interventions.

We conducted a retrospective matched case-control study using data from the Sistema de Informação de Agravos de Notificação database, involving adult patients with dengue who presented with warning signs or severe disease and were treated within Joinville's public health system (Sistema Único de Saúde) between January 2021 and December 2024. Cases were defined as fatal outcomes, while controls were matched survivors. Univariate and multivariate logistic regression models were used to estimate mortality risk.

Among 454 patients, 116 (26%) were cases and 336 (74%) were controls. Lower mortality was associated with having ≥ 2 medical consultations (odds ratio [OR] = 0.20; 95% confidence interval [CI]: 0.10-0.51) and receiving intravenous hydration of ≥ 1 L (OR = 0.32; 95% CI: 0.14-0.72). Hypotension (OR = 3.06; 95% CI: 1.33-7.03), thrombocytopenia (OR = 2.47; 95% CI: 1.21-5.02), and lethargy or irritability (OR = 15.59; 95% CI: 6.50-37.38) were significantly associated with mortality.

Early intravenous rehydration and repeated clinical evaluations were associated with reduced mortality. Close monitoring of patients with warning signs is crucial for improving outcomes in high-incidence settings.