A new model says COVID waves were driven more by the environment than by people catching it from each other.
March 19, 2026
Original Paper
SEVA: An externally driven framework for reproducing COVID-19 mortality waves without transmission feedback
medRxiv · 10.64898/2026.01.30.26345245
The Takeaway
Standard epidemiology assumes that disease waves grow and shrink based on the interaction between infected and susceptible people. This study introduces a framework where mortality curves are reproduced perfectly without any transmission feedback, suggesting that external environmental triggers, not human behavior or contagion levels, might be the primary driver of epidemic shapes.
From the abstract
Abstract Background COVID-19 epidemic waves display pronounced temporal structure in mortality, with substantial variation in wave shape, duration, and asymmetry across regions. These dynamics are commonly interpreted within transmission-based compartmental models, in which epidemic growth is driven by interactions between infectious and susceptible individuals. However, several empirical features of observed mortality curves, including prolonged declines, asymmetric wave shapes, and coheren