Detection of SARS-CoV-2 in aerosol and surface samples in high acuity hospital settings during community epidemic waves – implications for risk-based infection control

ABSTRACT

Rationale

Nosocomial transmission of SARS-CoV-2 is multifactorial and may vary between clinical sites.

Objectives

To measure SARS-CoV-2 in the air and on surfaces within the Intensive Care Unit (ICU) and Emergency Department (ED).

Methods

We conducted an air and surface-sampling study of SARS-CoV-2 in the ED and ICU of a hospital in Sydney.

Measurements

We sampled air, patient equipment, and personal protective equipment during two community COVID-19 epidemics. SARS-CoV-2 was detected using quantitative reverse transcription polymerase chain reaction (RT-qPCR). Carbon dioxide (CO2) was measured simultaneously, with <800 ppm indicating good air quality.

Main Results

SARS-CoV-2 genetic material was detected in 39% of 51 aerosol samples, with mean CO2 levels consistently <800 ppm for positive samples. The ED had more detections than the ICU (80% vs. 20%; p < 0.0027) and a higher mean CO2 level than the ICU (669 ppm vs. 522 ppm; p < 0.05). The ED waiting room, acute ward, and ICU staff tearoom showed higher detection rates than the ICU ward area. SARS-CoV-2 was detected in air samples in the ED a week before an outbreak was declared, and both inside and outside a COVID-19 patient's negative-pressure ICU room, where high-flow nasal prongs and a glove tested positive.

Conclusion

During community epidemics, SARS-CoV-2 genetic material is detected in hospital air despite good ventilation. Enhanced protection with masks, vaccines, and portable air purifiers, especially in high-risk areas, may mitigate nosocomial transmission, including among staff. Air sampling can provide an early warning of an outbreak and help identify areas that need enhanced infection control.