[Spread and persistence of chikungunya in the Brazilian Northeast (2015-2023): A spatiotemporal analysisAnálisis espaciotemporal de la expansión y la persistencia del chikunguña en el noreste de Brasil (2015-2023)].

OBJECTIVES

To analyze the spatiotemporal dynamics of chikungunya incidence in municipalities in the Brazilian Northeast from 2015 to 2023.

METHODS

Ecological time-series study of probable cases of chikungunya reported to Brazil's Notifiable Diseases Information System (SINAN). Monthly trends were assessed by joinpoint regression analysis with estimation of the monthly percent change (MPC) and 95% confidence intervals (95% CIs). High-risk space-time clusters were identified using a Poisson-based scan statistic (relative risk [RR], p < 0.05).

RESULTS

A total of 769 986 cases were reported in 2015-2023, mostly in the states of Ceará (27.9%), Bahia (25.3%), and Pernambuco (14.5%). Explosive outbreaks occurred in 2016, 2017, and 2022, interspersed with periods of low transmission. The temporal analysis revealed high initial MPC estimates, e.g., in Maranhão (127.4%; 95% CI: 112.5-172.6). In 2022, explosive outbreaks occurred once again, particularly in Alagoas (MPC = 342.4%; 95% CI: 187.2-557.3) and Piauí (MPC = 242.9%; 95% CI: 162.6-441.8). Significant space-time clusters were identified, 70% of which began in 2016. A disconnect was observed between geographic spread and magnitude of risk: the highest RR (45.5; 95% CI: 43.7-47.3) occurred in a cluster in Bahia in 2020, whereas the largest cluster involved 431 municipalities across four states in 2016.

CONCLUSION

The dynamics of chikungunya in the Brazilian Northeast were characterized by spatiotemporal heterogeneity, with shifting epicenters and persistent pockets of high risk, providing further evidence of the need for integrated, regionalized surveillance and control to address sustained transmission in high-risk pockets and interstate clusters.