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Airborne SARS-CoV-2 Detection by ddPCR in Adequately Ventilated Hospital Corridors
Joan Truyols-Vives1, Marta González-López1, Antoni Colom-Fernández1
1Molecular Biology, Health Geography, and One Health Research Group (MolONE), University of the Balearic Islands, 07122 Palma, Spain.
Abstract:
Indoors, the infection risk of diseases transmitted through the airborne route is estimated from indoor carbon dioxide (CO2) levels. However, the approaches to assess this risk do not account for the airborne concentration of pathogens, among other limitations. In this study, we analyzed the relationship between airborne SARS-CoV-2 levels and environmental parameters. Bioaerosols were sampled (n = 40) in hospital corridors of two wards differing in the COVID-19 severity of the admitted patients. SARS-CoV-2 levels were quantified using droplet digital PCR. SARS-CoV-2 was detected in 60% of the total air samples. The ward where the mildly ill patients were admitted had a higher occupancy, transit of people in the corridor, and CO2 levels, but there were no significant differences in SARS-CoV-2 detection between wards. The mean CO2 concentration in the positive samples was 569 ± 35.6 ppm. Considering all samples, the CO2 levels in the corridor were positively correlated with patient door openings but inversely correlated with SARS-CoV-2 levels. In conclusion, airborne SARS-CoV-2 can be detected indoors with optimal ventilation, and its levels do not scale with CO2 concentration in hospital corridors. Therefore, CO2 assessment should not be interpreted as a surrogate of airborne viral presence in all indoor spaces.
Insights
Indoor carbon dioxide (CO2) levels do not reliably indicate airborne SARS-CoV-2 presence. This study found CO2 levels were inversely correlated with virus detection, suggesting ventilation is key, not CO2 monitoring alone.
Area of Science:
- Environmental Science
- Infectious Disease Epidemiology
- Public Health
Background:
- Indoor carbon dioxide (CO2) levels are commonly used to estimate airborne infection risk.
- Current methods assessing airborne pathogen risk have limitations, including not accounting for pathogen concentration.
Purpose of the Study:
- To analyze the relationship between airborne SARS-CoV-2 levels and environmental parameters in hospital corridors.
- To investigate the utility of CO2 as a surrogate for airborne viral presence.
Main Methods:
- Bioaerosols were collected from hospital corridors (n=40) in wards with varying COVID-19 patient severity.
- SARS-CoV-2 RNA was quantified using droplet digital PCR.
- Environmental parameters including CO2 levels, occupancy, and people transit were recorded.
Main Results:
- SARS-CoV-2 was detected in 60% of air samples.
- No significant difference in SARS-CoV-2 detection was found between wards with differing patient severity.
- CO2 levels showed a positive correlation with patient door openings but an inverse correlation with SARS-CoV-2 levels.
Conclusions:
- Airborne SARS-CoV-2 can be detected in indoor environments with adequate ventilation.
- CO2 concentration is not a reliable indicator of airborne SARS-CoV-2 levels in hospital corridors.
- Relying solely on CO2 assessment may misrepresent airborne viral presence in indoor spaces.
