Viral sequencing reveals US healthcare personnel rarely become infected with SARS-CoV-2 through patient contact

Braun, Katarina M; Moreno, Gage K; Buys, Ashley; Somsen, Elizabeth D; Bobholz, Max; Accola, Molly A; Anderson, Laura; Rehrauer, William M; Baker, David A; Safdar, Nasia; Lepak, Alexander J; O’Connor, David H; Friedrich, Thomas C

BACKGROUND: Healthcare personnel (HCP) are at increased risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We posit current infection control guidelines generally protect HCP from SARS-CoV-2 infection in a healthcare setting. METHODS: In this retrospective case series, we use viral genomics to investigate the likely source of SARS-CoV-2 infection in HCP at a major academic medical institution in the Upper Midwest of the United States between 25 March - 27 December, 2020. We obtain limited epidemiological data through informal interviews and review of the electronic health record. We combine epidemiological information with healthcare-associated viral sequences and with viral sequences collected in the broader community to infer the most likely source of infection in HCP. RESULTS: We investigated SARS-CoV-2 infection clusters involving 95 HCP and 137 possible patient contact sequences. The majority of HCP infections could not be linked to a patient or co-worker (55/95; 57.9%) and were genetically similar to viruses circulating concurrently in the community. We found 10.5% of infections could be traced to a coworker (10/95). Strikingly, only 4.2% of HCP infections could be traced to a patient source (4/95). CONCLUSIONS: Infections among HCP add further strain to the healthcare system and put patients, HCP, and communities at risk. We found no evidence for healthcare-associated transmission in the majority of HCP infections evaluated here. Though we cannot rule out the possibility of cryptic healthcare-associated transmission, it appears that HCP most commonly becomes infected with SARS-CoV-2 via community exposure. This emphasizes the ongoing importance of mask-wearing, physical distancing, robust testing programs, and rapid distribution of vaccines.