Epidemiological and Temporal Modeling of Chikungunya in Maranhão: Trends, Seasonality, and Predictive Analysis (2019–2025)

Abstract

Introduction: Chikungunya fever is an arboviral disease transmitted by Aedes aegypti, causing significant suffering to the population and placing a substantial burden on healthcare services. Objective: To analyze the temporal trend and detection rate of Chikungunya in the state of Maranhão, Brazil, from 2019 to 2025. Methodology: This was an ecological time-series epidemiological study based on aggregated data obtained from the Notifiable Diseases Information System (SINAN), Ministry of Health. Results: Segmented trend analysis (Joinpoint) identified four distinct periods. Between 2019 and 2020, there was a sharp reduction in cases (APC = −74.5%), followed by a slight increase between 2020 and 2021 (APC = +10.7%). From 2021 to 2023, an exponential increase in cases was observed (APC = +297.5%), characterizing an epidemic outbreak. From 2023 onward, a consistent decline was observed through 2025 (APC = −44.4%). Discussion: The annual growth rate trend of Chikungunya cases showed an abrupt decrease in 2020, likely associated with the impact of the COVID-19 pandemic and consequent underreporting. The epidemic surge observed in 2022 revealed an extremely high increase (+1161%), culminating in a peak in 2023, followed by a decline during 2024–2025 and a consistent reduction in case numbers. Temporal trend analysis demonstrated a non-linear pattern with significant variations throughout the study period. Final Considerations: The simple linear regression model indicated an average increase of 357 cases per year; however, a poor fit was observed between estimated and actual values, with large residuals, particularly in 2020, 2022, and 2023, suggesting that the linear model is inadequate to describe the time series.