Early Warning Systems and Emergency Declarations During Brazil's Largest Dengue Outbreak

Area of Science:

• Public Health
• Epidemiology
• Health Governance

Background:

• Early warning systems (EWSs) are critical for managing public health emergencies.
• Brazil experienced its largest-ever dengue epidemic in 2024, providing a crucial test case for EWS effectiveness.
• Assessing the link between epidemic risk detection and governmental response is vital for improving public health preparedness.

Purpose of the Study:

• To evaluate the timeliness of public health emergency declarations (PHEDs) in Brazil during the 2024 dengue epidemic.
• To determine if epidemic severity and duration influenced the enactment of PHEDs.
• To identify factors, including political dynamics and primary health coverage, associated with PHEDs.

Main Methods:

• Data on dengue cases, deaths, and PHEDs were collected at federal, state, and municipal levels.
• Timeliness of declarations was assessed by mapping risk levels against 2023 and 2025 guidelines.
• Logistic regression models analyzed the association between epidemic severity and PHEDs, controlling for health coverage and political factors.

Main Results:

• The 2024 dengue epidemic escalated rapidly, with Brazil at alert level for 19 weeks and epidemic level for 11.
• Only 11 states and 7 capitals issued PHEDs, often after prolonged epidemic conditions, not early detection.
• Declaration timing was significantly linked to the duration of elevated risk, not political factors or primary health coverage.

Conclusions:

• Brazil's EWS framework was not sufficiently responsive to the rapid 2024 dengue epidemic.
• Strengthening responsive governance requires adaptive surveillance and institutional mechanisms for timely, coordinated responses.
• Decentralized decision-making and varying subnational capacities must be considered in improving public health emergency response.