Abstract: Background: Eight pm on April 13, 2022,a10:1 mixed test tube was found to be positive in the COVID-19 nucleic acid test site set up outside the hospital. In order to identify the infected case and control the spread of COVID-19 rapidly, we conducted this emergency investigation. Methods: According to the National COVID-19 Control and Prevention Protocol (8th edition), Guideline on Emergency Response to COVID-19 Case Found in Hospital in Shandong Province, and the Emergency Response Plan for COVID-19 in our hospital, information reporting, hospitalblockading, potential COVID-19 cases tracing, close contact screening, environmental sampling and disinfecting, COVID-19 nucleic acid testing and risk assessment were carried out by our team. Results: A female COVID-19 case aged 50 years was identified. She is aodd-jobber who works in the labour market near the hospital. The virus strain was sequenced as Omicron BA.2. A total of 65 close contacts was controlled in a hotel. The COVID-19 nucleic acid test results for all the staff of hospital, environmental samples were negative. The risk of COVID-19 spread was controlled and the hospital restarted of clinical activities as normal at 8 am on April 14 after blockaded for 12 hours. Inthe following 7 days, the staff of the hospital were tested for COVID-19 nucleic acid twice a day, and the results were negative. Then the testing frequency changed to once a day. Conclusion: Formulating detailed and feasible COVID-19 emergency response plans based on the requirements of the public documents and the actual conditions of the hospital, is useful to improve the efficiency of emergency response to COVID-19 cases and save time for control of COVID-19 spread and restart the clinical activities of hospital.

Key words: Covid-19, asymptomatic infection, emergency response