1/n My 2 cents:
According to @AdamJKucharski "the majority of secondary transmission may be caused by a very small fraction of individuals (80% of transmissions caused by ~10% of the total cases)". https://wellcomeopenresearch.org/articles/5-67  https://twitter.com/Dr_FarrisD/status/1265980949948444672

2/n What does this mean? My understand is: 10% had the luck to reach suitable environment - fertile breeding grounds, so to speak - to super-spread like wild fire. The latest cluster in SK shows #SARS_CoV2 is only 1 step away from hitting the jackpot. https://twitter.com/BBCLBicker/status/1265796157432754176?s=20

3/n The worst case scenario would be for #coronavirus to hop from one super-spreading setting to another, i.e., from nursing home to crowded living condition as in Montreal, from one club to another club as in Seoul, from hospitals to nursing homes as in NY.

4/n From the prevention standpoint, if a force should intervene to break the transmission chain (as barricading everyone inside their apartments bluntly did in Wuhan) and bust the cluster formation, the bulk of the transmission gets to be stopped.

5/n Clusters do form in Japan & SK as well, but they didn't go on and on because Japanese & Koreans
wore masks
did not hug or kiss on the cheek
obeyed stay-at-home & social distancing orders
traced cases & quarantined contacts
isolated symptomatic cases in hospitals

6/n NYC & Lombardy had none of the above. So that's 5 factors to add fuel to chain transmission & cluster formation instead of 5 factors to reduce transmission & put out the fire. Are we surprised that their case & death #'s exploded?

7/n Imagine if SK didn't madly trace, test & quarantine 83,000 contacts after 1 case in Seoul club. How many infections would those 247 cases generate in a month? Recall that according to @trvrb @nextstrain, the NYC outbreak was seeded multiple times. https://twitter.com/DrEricDing/status/1265156033531523073?s=20

8/n Japan did many things wrong: started late, insufficient testing, etc. But when it came to the most important thing - cluster busting (I love this phrase!) - Japan got it right. https://twitter.com/nataliexdean/status/1264376945468477440?s=20

9/n My main thanks go to the excellent thread by @nataliexdean https://twitter.com/nataliexdean/status/1263640768532619264?s=20