摘要
China has entered a new stage of COVID-19 epidemic prevention and control with emergence of the SARS-CoV-2 Omicron variant.This variant has a shorter incubation time and spreads more easily among humans.Since March 2022,cluster outbreaks of the Omicron variant in many parts of China spread undetected within the community for a period before being detected.The characteristics of the Omicron variant have made it difficult to implement early detection policies in Chinese cities.
