• Michael Klompas, Meghan A Baker, Chanu Rhee, Robert Tucker, Karen Fiumara, Diane Griesbach, Carin Bennett-Rizzo, Hojjat Salmasian, Rui Wang, Noah Wheeler, Glen R Gallagher, Andrew S Lang, Timelia Fink, Stephanie Baez, Sandra Smole, Larry Madoff, Eric Goralnick, Andrew Resnick, Madelyn Pearson, Kathryn Britton, Julia Sinclair, and Charles A Morris.
• Harvard Medical School, Harvard Pilgrim Health Care Institute, and Brigham and Women's Hospital, Boston, Massachusetts (M.K., M.A.B., C.R.).
• Ann. Intern. Med. 2021 Jun 1; 174 (6): 794-802.

BackgroundLittle is known about clusters of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in acute care hospitals.ObjectiveTo describe the detection, mitigation, and analysis of a large cluster of SARS-CoV-2 infections in an acute care hospital with mature infection control policies.DesignDescriptive study.SettingBrigham and Women's Hospital, Boston, Massachusetts.ParticipantsPatients and staff with cluster-related SARS-CoV-2 infections.InterventionClose contacts of infected patients and staff were identified and tested every 3 days, patients on affected units were preemptively isolated and repeatedly tested, affected units were cleaned, room ventilation was measured, and specimens were sent for whole-genome sequencing. A case-control study was done to compare clinical interactions, personal protective equipment use, and breakroom and workroom practices in SARS-CoV-2-positive versus negative staff.MeasurementsDescription of the cluster, mitigation activities, and risk factor analysis.ResultsFourteen patients and 38 staff members were included in the cluster per whole-genome sequencing and epidemiologic associations. The index case was a symptomatic patient in whom isolation was discontinued after 2 negative results on nasopharyngeal polymerase chain reaction testing. The patient subsequently infected multiple roommates and staff, who then infected others. Seven of 52 (13%) secondary infections were detected only on second or subsequent tests. Eight of 9 (89%) patients who shared rooms with potentially contagious patients became infected. Potential contributing factors included high viral loads, nebulization, and positive pressure in the index patient's room. Risk factors for transmission to staff included presence during nebulization, caring for patients with dyspnea or cough, lack of eye protection, at least 15 minutes of exposure to case patients, and interactions with SARS-CoV-2-positive staff in clinical areas. Whole-genome sequencing confirmed that 2 staff members were infected despite wearing surgical masks and eye protection.LimitationFindings may not be generalizable.ConclusionSARS-CoV-2 clusters can occur in hospitals despite robust infection control policies. Insights from this cluster may inform additional measures to protect patients and staff.Primary Funding SourceNone.

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