I don't think it's been quarantined well. In fact, I'd say the quarantine here in the US was handled very badly. Workers were exposed to quarantined individuals without proper equipment or training[0]. The virus has a long period before people show symptoms so the current number of people infected is probably larger and more widespread than we know.

[0] https://www.usnews.com/news/health-news/articles/2020-02-29/...