Study: SARS-CoV-2 RNA found in 39% of hospital air samples during outbreaks, despite good ventilation

COVID-19 genetic material was frequently detected in hospital air during community outbreaks, even in well-ventilated settings, according to a new study published in Respiratory Medicine.

A team led by Kirby Institute researchers conducted air and surface sampling in the emergency department (ED) and intensive care unit (ICU) of a large metropolitan hospital in Sydney, Australia, during two COVID-19 waves between November 2023 and July 2024. Their testing found that 39% (20 of 51) of aerosol samples were positive for SARS-CoV-2 RNA.

Detection was significantly more common in the ED than in the ICU. Of the positive samples, 80% were collected in the ED and 20% in the ICU. 

Hot spots within the ED included the acute-care area (9 of 13 samples positive), the public waiting room (6 of 12), and a walkway area (1 of 1). In the ICU, positive samples were detected in a staff tearoom (2 of 10), inside a negative-pressure room housing a COVID patient (1 of 1), and immediately outside that room (1 of 8).

“The higher rate of detection in the ED…suggests the ED carries a higher risk than the ICU, especially the public waiting room and acute care area,” write the authors. 

Aerosol testing may lead to early detection

Notably, four positive aerosol samples were collected in the ED from November 1 to November 7, 2023, which was up to a week before the hospital formally declared a multi-ward outbreak on November 8. These findings point to the potential value of using aerosol sampling to detect outbreaks before they become widespread, write the researchers.

Surface contamination was less common. Of 28 surface and equipment samples, 2 (7%) were positive. Both samples came from the room of an infected ICU patient.

During periods of high community epidemic activity, adequate air changes in the hospital ventilation system alone may not be enough to protect staff and patients

“During a rising epidemic wave of SARS-CoV-2 in the community, we found that over one-third of the aerosol samples tested positive for SARS-CoV-2 RNA in the ED and ICU environments, regardless of sampling duration and despite good ventilation within the hospital,” write the authors. “Although the presence of viral RNA in the air does not confirm infectiousness, the findings suggest during periods of high community epidemic activity, adequate air changes in the hospital ventilation system alone may not be enough to protect staff and patients from nosocomial [diseases acquired in a health care setting] transmission.”

HEPA filtration may help mitigate transmission

The findings underscore the importance of using high-efficiency particulate air (HEPA) filtration and ensuring staff have access to respiratory protection during outbreaks, particularly in high-traffic settings such as emergency departments, write the authors. They add that portable air purifiers and improved ventilation-system maintenance could further reduce the risk of transmission. 

They also stress the importance of mitigation strategies in ED waiting rooms, where patients and families often gather for hours and in which high-consequence pathogens such as SARS-CoV-2, influenza, and measles may be in high circulation.