4 1 The key population includes people with high exposure risk, high transmission risk and low resistance in COVID-19, including medical personnel, frontline personnel of entry and exit, customs and market supervision system, police, security guards, sanitation workers and cleaning staff.

According to the requirements of local towns and industry authorities, a 4 1 category key population nucleic acid detection account was established, and the nucleic acid detection was carried out in strict accordance with the prescribed frequency to ensure that all staff members "should check everything and not miss anyone". Staff who fail to carry out nucleic acid testing according to the prescribed frequency are not allowed to go to work in the unit, and should take the initiative to make up the test in time.

Transportation practitioners, couriers, service personnel in public places, water and electricity workers, the elderly, patients with chronic basic diseases, pregnant women, children, the disabled and other people.

Workers in transportation, loading and unloading, cleaning, security, sales, canteens and other positions in commercial enterprises are tested for 1 nucleic acid every 7 days; Other staff members conduct 1 nucleic acid testing every 7 days, and the sampling rate is not less than 1% each time. Those who have been included in the original 4 1 category, such as supermarket staff, should be tested for nucleic acid according to the original regulations.