Air, environmental sampling for COVID-19 around hospitalized patients

Editor's Note

This study led by researchers from the department of microbiology, Queen Mary Hospital, Hong Kong, found that COVID-19 RNA [ribonucleic acid] was not detectable by air samplers, suggesting that the airborne route is not the predominant mode of transmission.

The researchers sampled air close to six asymptomatic and symptomatic COVID-19 patients with and without surgical masks. Frequently touched environmental surfaces near 21 patients were swabbed before daily environmental disinfection. They then analyzed the correlation between the viral loads of patients’ clinical samples and environmental samples.

All air samples were negative for COVID-19 RNA for the six patients who were singly isolated inside airborne infection isolation rooms (AIIRS) with 12 air changes per hour.

Of 377 environmental samples taken from environmental surfaces near 21 patients, 19 were positive for COVID-19 by reverse-transcription polymerase chain reaction assay, with a median viral load of 9.2 x 10² copies/mL. Contamination was highest on patients’ mobile phones (7.8%), followed by bed rails (5.4%), and toilet door handles (5.3%).

There was a significant correlation between viral load ranges in clinical samples and positivity rates of environmental samples.

The researchers concluded that wearing a surgical mask, appropriate hand hygiene, and thorough environmental disinfection are sufficient infection control measures for COVID-19 patients isolated singly in AIIRS. This conclusion may not apply to aerosol-generating procedures or in wards with large numbers of COVID-19 patients.