Sources of exposure and risk among employees infected with severe acute respiratory coronavirus virus 2 (SARS-CoV-2) in a large, urban, tertiary-care hospital in the United States

Abstract

Objective: Hospital employees are at risk of SARS-CoV-2 infection through transmission in 3 settings: (1) the community, (2) within the hospital from patient care, and (3) within the hospital from other employees. We evaluated probable sources of infection among hospital employees based on reported exposures before infection.

Design: A structured survey was distributed to participants to evaluate presumed COVID-19 exposures (ie, close contacts with people with known or probable COVID-19) and mask usage. Participants were stratified into high, medium, low, and unknown risk categories based on exposure characteristics and personal protective equipment.

Setting: Tertiary-care hospital in Boston, Massachusetts.

Participants: Hospital employees with a positive SARS-CoV-2 PCR test result between March 2020 and January 2021. During this period, 573 employees tested positive, of whom 187 (31.5%) participated.

Results: We did not detect a statistically significant difference in the proportion of employees who reported any exposure (ie, close contacts at any risk level) in the community compared with any exposure in the hospital, from either patients or employees. In total, 131 participants (70.0%) reported no known high-risk exposure (ie, unmasked close contacts) in any setting. Among those who could identify a high-risk exposure, employees were more likely to have had a high-risk exposure in the community than in both hospital settings combined (odds ratio, 1.89; P = .03).

Conclusions: Hospital employees experienced exposure risks in both community and hospital settings. Most employees were unable to identify high-risk exposures prior to infection. When respondents identified high-risk exposures, they were more likely to have occurred in the community.

Fig. 1.

Approach to classifying the level of SARS-COV-2 exposure risk. Notably, participants could report exposures in multiple settings (ie, community and/or hospital (employee), and/or hospital (patient)), and in that case would be counted in multiple exposure groups. The classification scheme is presented for the hospital (employee) setting as an example; a similar approach to classification was used for the other 2 settings. Classification of risk in the patient setting assumed that all patients were unmasked and that aerosol-generating procedures conducted without a N95 mask (even if a non-N95 medical-grade mask was used) constituted a high-risk exposure. While providing patient care, masked exposures without eye protection, or with body contact while not wearing a gown and gloves, were also classified as low or intermediate risk. If a participant did not answer survey questions regarding exposures or masking, they were grouped into “exposure responses missing” and “masking responses missing” respectively. See supplementary text for more information about risk classification.