The definition of a close contact is getting broader in China, where authorities hunting down every potential COVID-19 infection now consider people who are far away and virtually unknown to each other as potentially at risk.
People who happen to be in the same general area at about the same time as a person who is found to be infected may need to be tested or even quarantined, according to notices issued by local health authorities. The "spacial-temporal overlap,” a term mentioned frequently by Chinese officials, means people don’t actually have to be in direct contact with a COVID-19 case to be impacted. Simply overlapping with someone carrying the virus is enough.
While authorities have been using mobile phone surveillance to identify close contacts throughout the pandemic, the latest effort appears to have expanded the criteria for contacts as the more infectious delta variant continues to spread. China has committed to fighting the virus at every step, and is taking more aggressive measures, including closing schools, entertainment venues and some forms of transportation, in its effort to regain a "Covid zero" status.