Sharing indoor space is a major SARS-CoV-2 infection risk. All identified outbreaks of three or more cases occurred in an indoor environment

By early April 2020, the COVID-19 pandemic had infected nearly one million people and had spread to nearly all countries worldwide. It is essential to understand where and how SARS-CoV-2 is transmitted.

Case reports from 320 municipalities in China were studied, not including Hubei province, between 4 January and 11 February 2020. All outbreaks involving three or more cases were studied

Three hundred and eighteen outbreaks with three or more cases were identified,involving 1245 confirmed cases in 120 prefectural cities.

The following chart indicates the environments where infections spread and the types of relationships between infectees. Refer to source for more detailed explanation.


Source: Indoor transmission of SARS-CoV-2, Hua Qian, Te Miao, Li LIU, Xiaohong Zheng, Danting Luo, Yuguo Li