Objective To strengthen prevention and control of nosocomial infections by retrospectively analyzing procedures of emergency responses to a patient with single IgM antibody positivity.Methods A feverish patient at the Department of Obstetrics and Gynecology in a tertiary hospital was found positive for the coronavirus IgM antibody during the active screening. A series of emergency responses were initiated immediately. The source of infection was blocked and the possible transmission routes were cut off. Epidemiological investigations were conducted to identify close contacts, throat swab samples were taken and the medical staff had their nucleic acid detected. Environmental samples at high-frequency contact points in the ward were collected to evaluate the disinfection effects of the hospital.Results After epidemiological investigations, 4 carers of patients and 59 medical staffs in the wards were determined as close contacts, all of whom tested negative for coronavirus. No positive cases for coronavirus were detected at the high-frequency contact points in the ward environment. Environmental cleaning and disinfection were effective and reliable. The warnings about potential nosocomial and community infections warnings were lifted. The prevention and control system was tested and flaws were also disclosed.Conclusions This case has provided useful reference for normalized hospital prevention and control and for quick restoration of normal medical order.