Investigation and emergency management of a nosocomial infection outbreak of Omicron BA.5.1.3 strain of SARS-CoV-2

OBJECTIVE To investigate a nosocomial infection outbreak of Omicron BA.5.1.3 strain of SARS-CoV-2, and to analyze the transmission mode of Omicron BA.5.1.3 strain in hospitals, in order to evaluate the effect of nosocomial infection control and provide a basis for the epidemic prevention and control of this strain in hospitals. METHODS The onsite epidemiological methods were used to investigate the confirmed cases and their close contacts, and the prevention and control measures of nosocomial infection caused by this outbreak were studied. RESULTS The outbreak time of nosocomial infection was from August 4 to August 8, and the incubation period was 1-5 days, with an average incubation period of 3.0 days. The first confirmed case was a 53-year-old woman who received three doses of COVID-19 vaccine and accompanied the family of the patient in the hospital. She had traveled to a high-risk area three days before onset of the disease, and the virus type was Omicron BA.5.1.3 strain. The outbreak area was two adjacent wards of the hospital, and the incidence rates of inpatients in the two wards were 66.67%（2/3） and 33.33%（1/3）, respectively. A total of 967 people were affected, including 1 imported case, 4 hospitalized cases（3 hospitalized patients and 1 nurse）, 537 close contacts and 425 secondary close contacts. On August 5, the city’s disease control and prevention telephone notified the first confirmed COVID-19 case. Within 0.5 hours, the ward where the case was located was sealed and static management was carried out. Measures such as district grid management, nucleic acid test in the whole hospital and in-hospital flow control were initiated. Environmental sampling, whole environment disinfection and telephone flow adjustment of case 1 were completed within 4 hours. Close contacts, secondary close contacts sampling and control were completed within 24 hours. We paid attention to the dynamics of close contacts and secondary close contacts, as if whose nucleic acid was positive, further measures could be taken to eliminate the risks. The hospital returned to normal management on August 13. CONCLUSION The novel coronavirus BA.5.1.3 strain shows strong pathogenicity, short incubation period, causing overall mild disease. Timely and comprehensive prevention and control measures were the key meathods to nosocomial infection control.