Investigation of the relation between risk assessment of exposure and nosocomial SARS-CoV-2 transmission in healthcare workers: a prospective single-centre study

Objectives Healthcare workers (HCWs) are among the risk groups for COVID-19. Determining transmission routes and risk levels during healthcare is of great importance in preventing nosocomial outbreaks. This study aimed to investigate the frequency of nosocomial transmission and factors affecting the transmission in HCW. Methods HCWs admitted to the infectious diseases outpatient clinic due to contact with a COVID-19 patient and diagnosed with SARS-COV-2 by reverse-transcriptase PCR (RT-PCR) between 20 March 2020 and 30 June 2020 were included in the study. Results A total of 822 HCWs with 295 low, 284 intermediate and 243 high-risk exposures were included in the study. 27.1% of the HCWs were male, and the median age was 31.9 years (20-62). 89.5% of these patients were directly in charge of patient care. Of the index cases contacted, 72.6% were HCW, and 27.4% were non-HCW patients. Most of the risky exposure (51.7%) occurred in nurses. The occurrence frequency of high-risk exposure was lower in those assigned to direct patient care when compared with the occurrence frequency of moderate-risk or low-risk exposures (76.5%, 94.7, 95.3, respectively p<0.001). In most high-risk exposures (220/253), the index cases were HCWs (p<0.001). Symptoms were detected in 311 of the HCWs (37.8%) during the follow-up. The median time to perform SARS-CoV-2 RT-PCR was 5.3 days (IQR) after the last risky exposure. In multivariate analysis, SARS-CoV-2 RT-PCR positivity was 5.65 times higher in HCWs not directly involved in patient care than HCWs who are not involved in patient care (95% CI 2.437 to 13.111; p<0.001). Conclusions This study provides particularly useful information on post-exposure COVID-19 follow-up and management of working schedules and procedures of HCWs.