Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark; Department of Science and Environment, Roskilde University, Universitetsvej 1, 4000 Roskilde, Denmark.
Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 Copenhagen, Denmark.
Epidemics. 2022 Sep;40:100613. doi: 10.1016/j.epidem.2022.100613. Epub 2022 Jul 30.
The SARS-CoV-2 ancestral strain has caused pronounced superspreading events, reflecting a disease characterized by overdispersion, where about 10% of infected people cause 80% of infections. New variants of the disease have different person-to-person variability in viral load, suggesting for example that the Alpha (B.1.1.7) variant is more infectious but relatively less prone to superspreading. Meanwhile, non-pharmaceutical mitigation of the pandemic has focused on limiting social contacts (lockdowns, regulations on gatherings) and decreasing transmission risk through mask wearing and social distancing. Using a mathematical model, we show that the competitive advantage of disease variants may heavily depend on the restrictions imposed. In particular, we find that lockdowns exert an evolutionary pressure which favours variants with lower levels of overdispersion. Our results suggest that overdispersion is an evolutionarily unstable trait, with a tendency for more homogeneously spreading variants to eventually dominate.
新冠病毒原始株引起了明显的超级传播事件，反映出疾病具有过度离散的特征，大约 10%的感染者引发了 80%的感染。疾病的新变体在病毒载量方面具有不同的人际间变异性，例如表明 Alpha（B.1.1.7）变体更具传染性，但相对不太容易发生超级传播。同时，大流行的非药物缓解措施侧重于限制社交接触（封锁、聚会规定）和通过戴口罩和保持社交距离降低传播风险。我们使用数学模型表明，疾病变体的竞争优势可能严重取决于施加的限制。特别是，我们发现封锁对具有较低过度离散水平的变体施加了进化压力。我们的结果表明，过度离散是一种进化上不稳定的特征，具有使更均匀传播的变体最终占主导地位的趋势。
