The staff of an isolated place in Chengdu was diagnosed. How was this staff member infected?

Guan Wei, the Chengdu Municipal Health and Wellness Committee, reported a newly confirmed case, which was a staff member in an isolation place. It is not clear how the worker was infected, but hundreds of volunteers are being quarantined. Several hotels in chenghua district have stayed in some centralized isolation personnel. Their main duty is to maintain order in isolated places and deal with some emergencies. There are hundreds of people working together. They work three shifts a day, take turns 24 hours a day, and don't go out at ordinary times.

There are 9 cases of asymptomatic infection/kloc-0 in this city, all of which are imported cases and are under centralized isolation medical observation. 4600 close contacts are under centralized isolation medical observation. Close contacts should be isolated from on-site staff. The nucleic acid test was negative before taking office. He works in an isolated place. Conventional nucleic acid tests were negative. The nucleic acid test was positive. After consultation by clinical expert group, it was diagnosed as a confirmed case. It has been transferred to a designated hospital for isolation treatment.

Preliminary investigation confirmed that this is related to the local confirmed cases found at the isolation site. Confirmed case 1, China nationality. Singapore flight ca404 arrived in Chengdu. After entering the country, they were concentrated and isolated. COVID-19 was diagnosed as asymptomatic infection due to positive nucleic acid test, and was transferred to a designated hospital for isolation treatment. Due to dry mouth, it was revised as a confirmed case. Confirmed case 2, China nationality. Egypt flight 3u8392 arrived in Chengdu and was quarantined after entry. Due to nasal congestion, hypoesthesia, runny nose, muscle aches, cough and runny nose, COVID-19 nucleic acid test was positive, and the case was diagnosed as a confirmed case and transferred to a designated hospital for isolation treatment.

Asymptomatic infection, China nationality. Egypt flight 3u8392 arrived in Chengdu and was quarantined after entry. COVID-19 was diagnosed as asymptomatic infection due to positive nucleic acid test, and was transferred to a designated hospital for isolation treatment. The isolation environment of confirmed cases and asymptomatic infected persons has been disinfected, and close contacts are in isolation observation state, and the nucleic acid test is negative.