This has happened at least twice before with a Chinese lab with SARS so it's not unknown. https://www.the-scientist.com/news-analysis/sars-escaped-beijing-lab-

This has happened at least twice before with a Chinese lab with SARS so it's not unknown. https://www.the-scientist.com/news-analysis/sars-escaped-beijing-lab-twice-50137 https://www.the-scientist.com/news-analysis/sars-escaped-bei... However the cases before, the virus was not new and the spread was quickly stopped.