ArticleFrontiers in public health2026
Semiannual seasonality of COVID-19 with alternating peaks in winter and summer.
Article in Frontiers in public health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
Objective: To examine the presence of seasonality and characterize the temporal epidemic patterns of COVID-19 incidence during the main pandemic period. Methods: The Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) method was used to systematically analyze COVID-19 incidence time series during the main pandemic period (March 1, 2020-February 28, 2023) from global, hemispheric, and key national perspectives. Results: Eight distinct epidemic waves occurred worldwide during the study period. The temporal pattern exhibited alternating peaks in winter and summer, corresponding to a semiannual cycle identified through time-series decomposition. This "winter-summer dual-peak" pattern was consistently observed across multiple spatial scales, although with regional variability in amplitude and timing. Conclusion: COVID-19 exhibited a clear semiannual seasonal pattern, differing from the typical unimodal winter dominance observed in many respiratory infectious diseases. This pattern may be associated with seasonal variations in environmental conditions. These findings may contribute to understanding the temporal dynamics of COVID-19 under normalized conditions and may provide reference for future studies on emerging respiratory infectious diseases.
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