A severe acute respiratory coronavirus virus 2 (SARS-CoV-2) nosocomial cluster with inter-facility spread: Lessons learned

Abstract

Background: Despite infection control guidance, sporadic nosocomial coronavirus disease 2019 (COVID-19) outbreaks occur. We describe a complex severe acute respiratory coronavirus virus 2 (SARS-CoV-2) cluster with interfacility spread during the SARS-CoV-2 δ (delta) pandemic surge in the Midwest.

Setting: This study was conducted in (1) a hematology-oncology ward in a regional academic medical center and (2) a geographically distant acute rehabilitation hospital.

Methods: We conducted contact tracing for each COVID-19 case to identify healthcare exposures within 14 days prior to diagnosis. Liberal testing was performed for asymptomatic carriage for patients and staff. Whole-genome sequencing was conducted for all available clinical isolates from patients and healthcare workers (HCWs) to identify transmission clusters.

Results: In the immunosuppressed ward, 19 cases (4 patients, 15 HCWs) shared a genetically related SARS-CoV-2 isolate. Of these 4 patients, 3 died in the hospital or within 1 week of discharge. The suspected index case was a patient with new dyspnea, diagnosed during preprocedure screening. In the rehabilitation hospital, 20 cases (5 patients and 15 HCWs) positive for COVID-19, of whom 2 patients and 3 HCWs had an isolate genetically related to the above cluster. The suspected index case was a patient from the immune suppressed ward whose positive status was not detected at admission to the rehabilitation facility. Our response to this cluster included the following interventions in both settings: restricting visitors, restricting learners, restricting overflow admissions, enforcing strict compliance with escalated PPE, access to on-site free and frequent testing for staff, and testing all patients prior to hospital discharge and transfer to other facilities.

Conclusions: Stringent infection control measures can prevent nosocomial COVID-19 transmission in healthcare facilities with high-risk patients during pandemic surges. These interventions were successful in ending these outbreaks.

Figure 1.

Epidemiology curve of nosocomial COVID-19 cases in the immune-suppressed ward at the University Hospital. The cluster occurred during July–August 2021. High-risk exposures were defined as being present during an aerosol-generating procedure without eye protection and a fit-tested N95 respirator or PAPR in the room of a patient diagnosed with laboratory-confirmed COVID-19 within the subsequent 10 days. *Patient 0 was diagnosed with nosocomial COVID-19 after a positive SARS-CoV-2 PCR test during prebronchoscopy screening for evaluation of dyspnea in an immunocompromised host. Although genetic sequencing was not available, it is possible that P0 was the cluster’s index case. **P4 is suspected to have been infected on the acute-care hospital immune-suppressed ward and subsequently to have become the index P1 patient in the rehabilitation hospital cluster (see Fig. 3). Because there were no known positive patients or HCWs from this unit during days 1–8, this time frame is not represented on the graph. No other nosocomial cases were identified for 8 months after day 29. Note. P, patient; H, healthcare worker.

Figure 2a.

Schematic representation of the cluster on the immune suppressed ward at the university hospital. Each patient is shown with their room location and the HCWs identified to have cared for them within 10 days prior to their positive test. Patients P1 and P4 resided in adjacent rooms. *Patient P3 initially resided in a room around the corner from P1 and P4 and was moved to a room farther apart 4 days prior to positive test. **HCWs H11, H14, and H15 worked on the ward, but direct exposures to any of the other infected patients or healthcare workers were not uncovered during the epidemiological investigation. P0, the first case of nosocomial SARS-CoV-2 acquisition on the unit, is not included in this figure because genetic sequencing was not available and no HCW was SARS-CoV-2 positive in connection with this case during contact tracing. Note. P, patient; H, healthcare worker.

Figure 2b.

Phylogenetic analysis of the patient and HCW samples from the immune suppressed ward at the university hospital. Because there were <2 mutation differences between these samples, they were considered to represent transmission of the same strain. Although further sequencing analysis revealed single amino acid changes in HCWs H7, H11, and H14 compared to the rest of the group, this is typical of the variation within the transmission cluster of a shared strain. Note. P, patient; H, healthcare worker.

Figure 3.

Epidemiological curve of nosocomial COVID-19 cases in the acute rehabilitation facility. The cluster was investigated during September–October 2021. After genetic sequencing results became available, patient P1 in this figure, the same as patient P4 from Figure 1, was retrospectively recognized as the common link that introduced the cluster strain into the rehabilitation facility during their admission in August. In the absence of rigorous surveillance at that time, it is likely that there was unrecognized nosocomial transmission within the facility during days 1–34 and that the size of the rehabilitation cluster has been underestimated. The isolates from the cases labeled with white squares either were not available for sequencing or could not be sequenced due to insufficient viral material, as was the case for HCWs rH10, rH11, rH12, rH13, who remained asymptomatic. HCW rH14 had community exposure, became symptomatic at home, and reported a subsequent SARS-CoV-2–positive test in the community, with clinical specimen unavailable for sequencing. Although HCW rH14 may not have been infected with the cluster strain, rH14 is included on the graph as the last positive case within a 14-day incubation period from last work shift within the rehabilitation facility. Note. rP, rehabilitation patient; rH, rehabilitation healthcare worker.