Case study from China: aerosol transmission can happen well over 2 meters. Like many other studies that have confirmed the virus is airborne, the case shows the inadequacy of the 2 meter rule. 1/N

A paper titled “A COVID-19 Outbreak — Nangong City， Hebei Province， China， January 2021”published by China CDC weekly in March 2021 detailed the epidemiological study of a outbreak of 76 cases, which was ignited by aerosol transmission over a distance of 4.5 meters. 2/N

Patient A was tested positive on January 2, 2021. Epidemiological tracing found that he met patient B on December 25, 2020 in a hospital in Shijiazhuang city. Genetic sequence confirmed that patient A got the virus from patient B. 3/N

CCTV video recording found that they were in the same room for 16 minutes, 4.5 meters apart. They did not talk to each other, or touch any common object. Patient B did remove her mask twice to eat something, afterwards Patient A removed his mask once to make a phone call. 4/N

Given Chinese hospitals are normally quite crowded, it is most likely that there were other people in the same room at that time period, fortunately no one else got infected, as most Chinese stick to masks rather rigorously where is required, especially at hospital settings. 5/N

By the time patient A was tested positive and quarantined, he already started a chain reaction in the community. By January 27, there were 76 confirmed cases in the city, eight generations of infection was observed in the chain of transmission, all originating from him. 6/N

Lesson from this study: with an airborne virus, there is nothing magic about the 2 meter rule. It is not fail-safe at all. While in the same room with other people, removing one's mask to eat, drink or make phone calls all create unnecessary risk. 7/N

With the outdated 2 meter rule, one wonders how many people got infected during coffee or lunch break at work places or schools. After all, the majority of cases can no longer be traced in Europe. 8/N

Dr. Eric Ding has an excellent thread about indoor air guidance for schools , which would be applicable for most work places as well
https://twitter.com/DrEricDing/status/1365678603212648461
Besides these institutional measures, here are some behavioral suggestion to reduce one's risk at workplaces or schools 9/N

1. When indoors, always mask up. Exceptions should be as few as possible, because the virus makes no exception for us.
2. When conditions allows it, eat or drink outdoors, keep the distance from each other.
10/N

3. If one has to eat indoors (say, on a rainy day), do it in a separate room, ventilate the room thoroughly before and after. 10/N last of this thread