(1) key places. Stations, ports, airports, docks, public transport (cars, trains, airplanes, subways), logistics parks, nucleic acid detection points, farmers' (bazaars) markets, hotels, shopping malls, supermarkets, fitness and entertainment places, hairdressing and bathing places, theaters, stadiums, libraries, museums and other places with dense people and closed spaces are prone to cluster epidemics.

(2) Key institutions. Institutions that maintain the normal operation of society or are prone to cluster epidemics include party and government organs, enterprises and institutions, medical institutions, service institutions in the field of child welfare, nursing homes, nursing homes, supervision places, colleges and universities, primary and secondary schools, kindergartens, training institutions, labor-intensive enterprises, construction sites, etc.

(3) key groups. Staff in key places and institutions, people with high risk of infection or low resistance, including medical personnel, front-line personnel of entry and exit, customs and market supervision system, police, sanitation workers, security guards and cleaners, port transport practitioners, couriers, water and electricity workers, home isolation medical observation or home health monitoring personnel, rescuers in local epidemic areas, epidemic prevention and control personnel, vagrants and beggars, and scattered decoration and construction personnel.