Environmental surveillance of SARS-CoV-2 for outbreak detection in hospital: A single centre prospective study

Background

Healthcare facilities remain at risk of Coronavirus Disease 2019 (COVID-19) outbreaks. Proactive surveillance strategies can potentially mitigate the risk of these outbreaks.

Objective

To determine whether results from the environmental detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) from floor swabs could be provided to the Infection Prevention and Control (IPAC) team in near real-time.

Methods

We conducted a 9-week prospective study at a rehabilitation hospital in Toronto, Canada. Beginning in October 2023, we swabbed the hallways and adjoining areas of one of the floors of the hospital. This floor consisted of two separate units: the Medical Rehab Unit and the Transitional Care Unit, each accommodating 32 patients. Swabs were assayed for SARS-CoV-2 by quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR). Results from the floor swabs, including percentage positivity for SARS-CoV-2 and number of viral RNA copies, were sent to the hospital's infection control team twice-weekly. Number of patients with COVID-19, confirmed and suspected COVID-19 outbreaks, and acute transfers to another hospital were recorded over the study duration.

Results

A total of 465 swabs were collected, and 232 (50%) were positive for SARS-CoV-2. The turnaround time from floor swabbing to the results being provided to IPAC ranged from 1–6 days with an average turnaround time of 1.9 days (interquartile range: 1 to 2 days). Swab positivity in the Medical Rehab Unit (65%, 95% CI: 58–71%) was significantly greater than the Transitional Care Unit (38%, 95% CI: 32–44%). During the study period there were 4 patients diagnosed with COVID-19 on the Medical Rehab Unit and none on the Transitional Care Unit. There was one suspected COVID-19 outbreak on the Medical Rehab Unit: three COVID-19 cases were identified within six days; all patients on the unit were tested for COVID-19; no further cases were identified and no outbreak was declared. During the suspected outbreak, the percentage of floor swabs positive for SARS-CoV-2 peaked, at 100% in the Medical Rehab Unit.

Conclusion

Floor swabs were provided to IPAC in almost real-time; however, delays in shipments in some instances led to delays in the results being made available. Larger studies over an extended timeframe are needed to better understand whether environmental surveillance can aid IPAC decision-making.