Transport of Aerosols/Droplets Related to the Spread of COVID-19 in Indoor and Outdoor Environments

随着对如何最大限度地减少和控制COVID-19的认识的提高，阿尔伯塔省等许多地方正在逐步重新启动经济。这包括在不久的将来重新开放餐馆、公园和零售企业，以及学校。公园、游泳池和海滩等许多地方都出现了拥挤现象。目前的2米社交距离可能只适用于大的呼吸道飞沫，而携带病毒的小气溶胶可以在空气中悬浮很长时间并传播很远的距离（例如，最近的一项研究表明，即使没有风，也可以传播7-8米）。鉴于COVID-19病毒可以在气溶胶中保持数小时的传染性，并且感染可能仅由一种病毒引起，因此研究小气溶胶的运输是必要的。公共卫生决策者特别面临以下紧迫问题：(a)在不同的室内和室外条件下，呼吸道气溶胶/飞沫的运输风险是什么？（二）本港特有的气候对交通有何影响？(c)对于在这种情况下聚集的人，应该制定什么样的公共政策？

With the improving knowledge of how to minimize and control of COVID-19, many places such as Alberta are gradually relaunching the economy. This includes re-opening restaurants, parks and retail businesses, as well as schools in the near future. Crowding has been seen in many places such as parks, swimming pools and beaches. The current 2 m social distancing is likely only derived for large respiratory droplets, while virus-laden small aerosols can be suspended in air for a long time and travel large distances (e.g., 7-8 m even without wind in a recent study). Given that COVID-19 virus can remain infective for hours in aerosols and infection can be caused just by one virus, it is imperative to study the transport of small aerosols. Public health policy makers are specifically facing the following urgent questions (a) what are the transport risks of respiratory aerosols/droplets in different indoor and outdoor conditions? (b) what are the impacts of local specific climate on the transport? And (c) what public policy should be made on people gathering in these conditions? This research will provide the scientific foundation to answer these questions. Specifically, this research will focus on the transport of droplets/aerosols generated by talking, singing, coughing, and sneezing in different indoor (heating, ventilation, and air conditioning) and outdoor (wind speed and direction) conditions and with preventive measures (plastic shields), using computational fluid dynamics modeling. The research will also assess the spreading risks of COVID-19 under various social gathering scenarios and suggest potential government policies, based on the modeling results. This research is expected to have a significant impact to Alberta Health and others in updating/making effective policies in stopping the spread of COVID-19, guiding the relaxation of COVID-19 restrictions, and better preparing Canadians for the potential next wave of COVID-19 or similar pandemics in the future.