论文标题
消除COVID-19：旅行和时机的影响
Eliminating COVID-19: The Impact of Travel and Timing
论文作者
论文摘要
我们通过考虑疾病在区域内部和地区之间的个体之间的传播来分析Covid-19的传播。一组地区可以定义为人口的任何分区，使每个地区内的旅行/社会接触远远超过了他们之间的旅行/社交接触。如果区域到区域生殖数字可以消除COVID-19。单个感染区域将传播病毒的其他区域的平均数量减少到小于一个。我们发现，在施加区域级别控制措施之前，该区域到区域的生殖数与区域之间的旅行率和指数长度的指数成倍成正比。因此，降低旅行和区域扮演行动发挥作用决定性作用的速度在是否从一系列地区消除了Covid-19。如果平均而言，感染的区域（包括将来被重新感染的区域）在积极扩散开始后不久就会采取社会距离措施，则感染区域的数量以及所需的措施的区域数量将随着时间的推移而成倍地减少。在这种情况下，即使在大多数地区取消了社会距离措施之后，淘汰也将是一个稳定的固定点。
We analyze the spread of COVID-19 by considering the transmission of the disease among individuals both within and between regions. A set of regions can be defined as any partition of a population such that travel/social contact within each region far exceeds that between them. COVID-19 can be eliminated if the region-to-region reproductive number---i.e. the average number of other regions to which a single infected region will transmit the virus---is reduced to less than one. We find that this region-to-region reproductive number is proportional to the travel rate between regions and exponential in the length of the time-delay before region-level control measures are imposed. Thus, reductions in travel and the speed with which regions take action play decisive roles in whether COVID-19 is eliminated from a collection of regions. If, on average, infected regions (including those that become re-infected in the future) impose social distancing measures shortly after active spreading begins within them, the number of infected regions, and thus the number of regions in which such measures are required, will exponentially decrease over time. Elimination will in this case be a stable fixed point even after the social distancing measures have been lifted from most of the regions.
