Ensemble Forecast Projects About 860,000 Dengue Cases in Brazil for 2027

Overview

• An open, multi‑team forecasting exercise presented on Nov. 6 put the ensemble median at roughly 860,000 probable dengue cases for the 2027 season with an 80% uncertainty range of 560,000 to 1.6 million and a projected weekly peak near 40,000 cases in April.
• Researchers said the projection does not point to an epidemic on the scale of 2024 but warned that dengue remains endemic and that health services must prepare to manage sustained case volumes and severe patients.
• Only a few models in the challenge included climate variables and those models disagreed, so teams recommended treating the expected strong El Niño as a contingency trigger and using short‑term forecasts to track any climate‑driven changes.
• The ensemble flagged state‑level increases in Paraná, Rio de Janeiro, Mato Grosso do Sul, Sergipe, Acre and Minas Gerais and also projected more than 90,000 probable chikungunya cases, which will raise demands on clinics where both viruses circulate.
• The InfoDengue–Mosqlimate challenge pooled 22 models from 27 teams to produce a combined forecast intended to support anticipatory planning and not replace routine surveillance, and experts urged simple prevention measures such as eliminating standing water and early clinical care seeking.