As of this moment, large-scale group quarantines are the only mitigation measures that have been shown to reduce the R0 of the coronavirus below 1. (The source

As of this moment, large-scale group quarantines are the only mitigation measures that have been shown to reduce the R0 of the coronavirus below 1. (The source for this is a recent epidemiological study of the situation in Wuhan: https://www.medrxiv.org/content/10.1101/2020.03.03.20030593v1 https://www.medrxiv.org/content/10.1101/2020.03.03.20030593v...) Given this, it's perhaps understandable that governments and individuals in the hardest-hit areas would be erring on the side of caution.