What do you mean by high risk in closed-loop operation?

Employees in high-risk positions should work in a closed loop. Mainly refers to people who are in direct contact with entry personnel and articles, including imported cold chain goods and environment, staff in centralized isolation places, medical staff in designated medical institutions and fever clinics of comprehensive medical institutions, etc. Employees in these positions are required to work in a closed loop, strictly implement personal protection and nucleic acid detection to prevent "damage".