Potential impact of seasonal forcing on a SARS-CoV-2 pandemic

Richard A Neher; Robert Dyrdak; Valentin Druelle; Emma B Hodcroft; Jan Albert

To explore possible scenarios more systematically, we ran such simulations for a range of values for R 0 and peak transmissibility θ and recorded whether we observe and early peak, a late peak, or a two peaks. The right panel of Fig. 3 shows the ratio of the height of these peaks for different values. Rapid growth (high R 0 ) and late transmission peaks result in a large peak in the first half 2020, while lower R 0 and transmission peaks in early winter favor a large secondary peak. These two scenarios are separated by a band of parameter values that give rise to two pandemic waves in the winters of 2020 and 2021 in the Northern Hemisphere. Individual trajectories for a variety of parameter combinations are given in Fig. S4 . The qualitative behavior is robust to model perturbations and parameter variation as long as seasonal forcing is strong. With weak forcing (ε = 0.15), the model predicts a single peak for most combinations of R 0 and migration rates (see Fig. S5 ).