Abstract: Background：As Omicron variant is extremely infectious, the pandemic of Omicron variant in Shanghai from March to May this year is complex, dynamic and uncertain, therefore it is more challenging for hospitals. Objective：To summarize the experience of bubble management of preventing and controlling nosocomial infection and occupational exposure of COVID19. Design：Observational study. Methods：In this pandemic, our hospital is designed as a big bubble. Six key medical departments are designed as medium bubbles, including the outpatient of COVID19, fever clinic, emergency department, special ward of COVID19, neonatal isolation ward and transition ward. Several important departments of medium bubbles are designed as small bubbles. Those with a red code, positive results of coronavirus nucleic acid or antigen tests, or infection history of COVID19, and the close contacts of COVID19 were admitted to the outpatient of COVID19. According to the condition and epidemic history, they were arranged to different functional small bubbles. Those fever patients with a green code or a yellow code were admitted to fever clinic. Those with emergent conditions but without fever were admitted to the emergency department which was further divided into two small bubbles named as the buffer area and general area . The backup was also available. Patients with a positive PCR result were admitted to the special ward of COVID19 while those with severe critical illness were in the ICU, and the other with mild or common type were in the general ward. All newly admitted children except critical illness and neonates were in the transition ward. Neonates with negative primary screening nucleic acid from pregnant women with COVID19 were admitted to neonatal isolation ward while all neonates were arranged in the small bubble of negative pressure area first. After daily nucleic acid tests for 3 days, those with negative resulst were transferred to nonnegative pressure area and the other with positive results were transferred to special ward of COVID19. The flow of personnel and meterial with different risk rate was not allowed. The staff with the lower risk moving to the higher level risk should be reported to the department of medical affairs. Meanwhile the plan of the bubble burst is ready. Standard training contents and assessment requirements were formulated according to different posts of staff, and checked through voice and video monitoring system and onsite supervision. Main outcome measures：Nosocomial infection and occupational exposure of COVID19. Results：A total of 432 patients with COVID19 were admitted to our hospital, including 341 patients with mild type (78.9%), 88 patients with common type(20.4%), and 3 patients with critical illness. Each critical illness had invasive mechanical ventilation while one patient had additional CRRT and ECMO .None of them died from COVID19. Twentynine patients had underlying disease and 109 staff successively worked in outpatient and inpatient of COVID19 including 46 doctors, 49 nurses, 9 medical technicians and 5 auxiliary medical personnel, none of which had nosocomial infection and occupational exposure of COVID19. A total of 189 persons with a red code were intercepted at the entrance of the hospital. All patients with red codes were guided to the outpatient of COVID19, therefore, none of them was permitted into the general outpatient and emergency department. The total number of outpatient and emergency patients was 253 571, 12 114 of which was admitted to emergency. Six emergency patients were positive of primary nucleic acid test. Three patients with COVID19 entered the general area of emergency, resulting in the closed disinfection and sterilization for 3 times, activating the backup emergency area. A total of 8 328 patients were admitted to fever clinic, 50 of which were transferred to the outpatient of COVID19 after positive nucleic acid test. The total number of outpatient of COVID19 was 763. According to grade V triage,3 of 4 cases of grade I /II were critical illness. In total, 690 neonates were admitted to our hospital including 516 cases of lowrisk epidemic history and 174 cases of highrisk epidemic history, 2 cases of which were positive of nucleic acid test. Six hundred and ninetythree patients were admitted to the transition ward including 223 emergency cases and 470 selective cases, 1 of which was positive of nucleic acid test. All staff working in the isolation ward participated in theoretical training and special training on highrisk bubbles was carried out for 29 times for 291 people. Both theoretical training and operation training were qualified.Video monitoring and onsite supervision were performed for 304 people. Conclusion：There was neither nosocomial infection nor cupational exposure of COVID19 in this bubble management.

Key words: SARS-CoV-2, Bubble management, Nosocomial infection, Occupational exposure