论文标题
二次增长在19009年大流行期间：合并热点和恢复
Quadratic growth during the COVID-19 pandemic: merging hotspots and reinfections
论文作者
论文摘要
在大流行的早期，通常将指数增长阶段的存在通常被认为是理所当然的。然而，对于2019年新型冠状病毒流行病，早期指数阶段仅持续了大约六天，而二次增长持续了40天，直到它扩散到其他国家并继续延续，并又是四边形，但具有更大的系数。在这里，我们证明了这个快速阶段之后是随后的降低，其中系数降低至爆发时几乎原始值。这可以通过在疾病跳跃（非局部）与相对较少数量的分离地点后发生的先前断开的位点的合并来解释。随后的坡度随着持续增长的变化可以定性地解释，这是由于其恢复和速率变化而导致的。我们证明，观察到的行为可以通过标准的流行病学模型来描述，并包括空间范围和重新感染。空间扩散系数的时间相关变化还可以模拟斜率中的相应变化。
The existence of an exponential growth phase during early stages of a pandemic is often taken for granted. However, for the 2019 novel coronavirus epidemic, the early exponential phase lasted only for about six days, while the quadratic growth prevailed for forty days until it spread to other countries and continued, again quadratically, but with a larger coefficient. Here we show that this rapid phase is followed by a subsequent slow-down where the coefficient is reduced to almost the original value at the outbreak. This can be explained by the merging of previously disconnected sites that occurred after the disease jumped (nonlocally) to a relatively small number of separated sites. Subsequent variations in the slope with continued growth can qualitatively be explained as a result of reinfections and changes in their rate. We demonstrate that the observed behavior can be described by a standard epidemiological model with spatial extent and reinfections included. Time-dependent changes in the spatial diffusion coefficient can also model corresponding variations in the slope.
