Patient and ward related risk factors in a multi-ward nosocomial outbreak of COVID-19: Outbreak investigation and matched case-control study

Jenine Leal; Heidi M O'Grady; Logan Armstrong; Devika Dixit; Zoha Khawaja; Kate Snedeker; Jennifer Ellison; Joyce Erebor; Peter Jamieson; Amanda Weiss; Daniel Salcedo; Kimberley Roberts; Karen Wiens; Matthew A Croxen; Byron M Berenger; Kanti Pabbaraju; Yi-Chan Lin; David Evans; John M Conly

doi:10.1186/s13756-023-01215-1

Patient and ward related risk factors in a multi-ward nosocomial outbreak of COVID-19: Outbreak investigation and matched case-control study

Antimicrob Resist Infect Control. 2023 Mar 22;12(1):21. doi: 10.1186/s13756-023-01215-1.

Authors

Jenine Leal^{1

2

3

4}, Heidi M O'Grady¹, Logan Armstrong⁵, Devika Dixit⁶, Zoha Khawaja⁷, Kate Snedeker⁸, Jennifer Ellison⁹, Joyce Erebor¹, Peter Jamieson¹⁰, Amanda Weiss¹¹, Daniel Salcedo¹¹, Kimberley Roberts¹¹, Karen Wiens¹¹, Matthew A Croxen^{12

13

14

15}, Byron M Berenger^{16

17}, Kanti Pabbaraju¹⁷, Yi-Chan Lin^{12

18}, David Evans^{12

18}, John M Conly^{19

20

21

22

23

24

25

26}

Affiliations

¹ Infection Prevention and Control, Alberta Health Services, Calgary, AB, Canada.
² Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
³ O'Brien Institute for Public Health, University of Calgary and Alberta Health Services, Calgary, AB, Canada.
⁴ Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB, Canada.
⁵ Infection Prevention and Control, Alberta Health Services, Edmonton, AB, Canada.
⁶ Department of Pediatrics, Division of Infectious Diseases, University of Calgary and Alberta Health Services, Calgary, AB, Canada.
⁷ W21C, Department of Medicine, University of Calgary, Calgary, AB, Canada.
⁸ Provincial Population and Public Health, Alberta Health Services, Calgary, AB, Canada.
⁹ Infection Prevention and Control, Alberta Health Services, Lethbridge, AB, Canada.
¹⁰ Department of Family Medicine, University of Calgary and Alberta Health Services, Calgary, AB, Canada.
¹¹ Cardiac Sciences, Foothills Medical Centre, Alberta Health Services, Calgary, AB, Canada.
¹² Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada.
¹³ Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada.
¹⁴ Women and Children's Health Research Institute, University of Alberta, Edmonton, AB, Canada.
¹⁵ Alberta Public Health Laboratory, Alberta Precision Laboratories, Edmonton, AB, Canada.
¹⁶ Department of Pathology and Laboratory Medicine, University of Calgary and Alberta Health Services, Calgary, AB, Canada.
¹⁷ Alberta Public Health Laboratory, Alberta Precision Laboratories, Calgary, AB, Canada.
¹⁸ Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada.
¹⁹ Infection Prevention and Control, Alberta Health Services, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²⁰ Department of Medicine, Cumming School of Medicine, University of Calgary and Alberta Health Services, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²¹ O'Brien Institute for Public Health, University of Calgary and Alberta Health Services, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²² Department of Microbiology, Immunology and Infectious Diseases, University of Calgary, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²³ Department of Pathology and Laboratory Medicine, University of Calgary and Alberta Health Services, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²⁴ Synder Institute for Chronic Diseases, University of Calgary and Alberta Health Services, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²⁵ W21C, Department of Medicine, University of Calgary, Calgary, AB, Canada. John.Conly@albertahealthservices.ca.
²⁶ Foothills Medical Centre, AGW5 - Special Services Bldg, 1403 29Th Street Nw, Calgary, AB, T2N 2T9, Canada. John.Conly@albertahealthservices.ca.

Abstract

Background: Risk factors for nosocomial COVID-19 outbreaks continue to evolve. The aim of this study was to investigate a multi-ward nosocomial outbreak of COVID-19 between 1st September and 15th November 2020, occurring in a setting without vaccination for any healthcare workers or patients.

Methods: Outbreak report and retrospective, matched case-control study using incidence density sampling in three cardiac wards in an 1100-bed tertiary teaching hospital in Calgary, Alberta, Canada. Patients were confirmed/probable COVID-19 cases and contemporaneous control patients without COVID-19. COVID-19 outbreak definitions were based on Public Health guidelines. Clinical and environmental specimens were tested by RT-PCR and as applicable quantitative viral cultures and whole genome sequencing were conducted. Controls were inpatients on the cardiac wards during the study period confirmed to be without COVID-19, matched to outbreak cases by time of symptom onset dates, age within ± 15 years and were admitted in hospital for at least 2 days. Demographics, Braden Score, baseline medications, laboratory measures, co-morbidities, and hospitalization characteristics were collected on cases and controls. Univariate and multivariate conditional logistical regression was used to identify independent risk factors for nosocomial COVID-19.

Results: The outbreak involved 42 healthcare workers and 39 patients. The strongest independent risk factor for nosocomial COVID-19 (IRR 3.21, 95% CI 1.47-7.02) was exposure in a multi-bedded room. Of 45 strains successfully sequenced, 44 (97.8%) were B.1.128 and differed from the most common circulating community lineages. SARS-CoV-2 positive cultures were detected in 56.7% (34/60) of clinical and environmental specimens. The multidisciplinary outbreak team observed eleven contributing events to transmission during the outbreak.

Conclusions: Transmission routes of SARS-CoV-2 in hospital outbreaks are complex; however multi-bedded rooms play a significant role in the transmission of SARS-CoV-2.

Keywords: COVID-19; Case–control; Environment; Incidence density sampling; Nosocomial; Outbreak; Rate ratio; Risk factors; Viral culture.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Alberta
COVID-19* / epidemiology
Case-Control Studies
Cross Infection* / epidemiology
Cross Infection* / prevention & control
Disease Outbreaks
Humans
Retrospective Studies
Risk Factors
SARS-CoV-2 / genetics
Tertiary Care Centers