Defining boundaries

Late on Jan 20, the Shanghai Cancer Center Affiliated with Fudan University reported a "suspicious result "for an outsourced logistics worker at the facility during nucleic acid testing conducted on staff members.

Immediately after receiving this information in a phone call, Zhang and other health officials, experts and pandemic control workers rushed to a local disease control and prevention center, where they worked throughout the night.

Tracing and screening the logistics worker's close contacts began straight after the suspicious test result was obtained, along with an epidemiological investigation.

"If we had started this work just one minute later, there may have been one more route in which the virus could have spread, which would need to be tracked, but getting on top of the situation immediately enabled us to take the initiative in pandemic prevention and control," Zhang said.