Every single person in China who seeks medical care and who has fever or respiratory symptoms is tested. Every person who works in a high-risk job (e.g., airpo

Every single person in China who seeks medical care and who has fever or respiratory symptoms is tested. Every person who works in a high-risk job (e.g., airport staff, border staff, some types of medical personnel) is regularly tested. Purchases of over-the-counter fever-reducing drugs are monitored. That's how outbreaks are caught early. If you're interested, and if you read Chinese, you can actually learn in great detail how (almost) each outbreak over the last year-plus was detected. There are detailed contact-tracing reports on most of the outbreaks.