A study of hospital air contamination has found that 17.4% of air samples from environments near COVID-19 patients were positive for SARS-CoV-2 RNA, the virus that causes COVID-19, but only 8.6% contained viable virus.
Researchers at Imperial College London, Centre Hospitalo-Universitaire de Nantes, INSERM, Assistance Publique–Hôpitaux de Paris, Hôpital Bichat–Claude Bernard and Universitaire Paris Diderot, reviewed 24 observational studies of air contamination in hospital settings from 1 January to 27 October with data on SARS-CoV-2 viral RNA positivity rates detected by reverse-transcription polymerase chain reaction (RT-PCR), viral culture, air ventilation systems, and distance from patients.
Overall, 82 of 471 air samples (17.4%) from close patient environments (within 5 meters) were positive for SARS-CoV-2 RNA, with no significant difference associated with distance from patients. The positivity rate in intensive care settings was 25.2% (27 of 107 samples) compared with 10.7% (39 of 364 samples) for non-intensive care units (P < .001).
Of a total of 81 viral cultures performed, 7 (8.6%) were positive, all from close patient settings. The authors note that this finding is consistent with studies of other respiratory viruses that are frequently found in the air around patients, but which rarely demonstrate the presence of viable viruses.
Public areas showed high viral loads, with 56.3% of hallway samples testing positive and a 33.3% public area positivity rate overall. High viral loads were also found in patient bathrooms (23.8% positivity rate), staff workstations (27.2%), and staff meeting rooms (19.2%).
"In an epidemic setting, public areas are often crowded, with both a high patient flow and high incidence of COVID-19," the authors wrote. "These factors have to be considered to control the transmission of COVID-19 between non-masked HCPs in hospitals, especially staff rooms and lockers."
The study authors point to wide variability in the air sampling methods and poorly detailed climatic conditions such as temperature and humidity – that can affect the capacity for viral particles to remain suspended in air – as factors that limit the study's conclusions and call for further research.
Study details
Assessment of Air Contamination by SARS-CoV-2 in Hospital Settings
Gabriel Birgand; Nathan Peiffer-Smadja; Sandra Fournier; Solen Kerneis; François-Xavier Lescure; Jean-Christophe Lucet
Published in JAMA Network Open on 23 December 2020
Abstract
Importance
Controversy remains regarding the transmission routes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Objective
To review current evidence on air contamination with SARS-CoV-2 in hospital settings and the factors associated with contamination, including viral load and particle size.
Evidence Review
The MEDLINE, Embase, and Web of Science databases were systematically queried for original English-language articles detailing SARS-CoV-2 air contamination in hospital settings between January 1 and October 27, 2020. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The positivity rate of SARS-CoV-2 viral RNA and culture were described and compared according to the setting, clinical context, air ventilation system, and distance from patients. The SARS-CoV-2 RNA concentrations in copies per meter cubed of air were pooled, and their distribution was described by hospital areas. Particle sizes and SARS-CoV-2 RNA concentrations in copies or median tissue culture infectious dose (TCID50) per meter cubed were analyzed after categorization as less than 1 μm, from 1 to 4 μm, and greater than 4 μm.
Findings
Among 2284 records identified, 24 cross-sectional observational studies were included in the review. Overall, 82 of 471 air samples (17.4%) from close patient environments were positive for SARS-CoV-2 RNA, with a significantly higher positivity rate in intensive care unit settings (intensive care unit, 27 of 107 [25.2%] vs non–intensive care unit, 39 of 364 [10.7%]; P < .001). There was no difference according to the distance from patients (≤1 m, 3 of 118 [2.5%] vs >1-5 m, 13 of 236 [5.5%]; P = .22). The positivity rate was 5 of 21 air samples (23.8%) in toilets, 20 of 242 (8.3%) in clinical areas, 15 of 122 (12.3%) in staff areas, and 14 of 42 (33.3%) in public areas. A total of 81 viral cultures were performed across 5 studies, and 7 (8.6%) from 2 studies were positive, all from close patient environments. The median (interquartile range) SARS-CoV-2 RNA concentrations varied from 1.0 × 103 copies/m3 (0.4 × 103 to 3.1 × 103 copies/m3) in clinical areas to 9.7 × 103 copies/m3 (5.1 × 103 to 14.3 × 103 copies/m3) in the air of toilets or bathrooms. Protective equipment removal and patient rooms had high concentrations per titer of SARS-CoV-2 (varying from 0.9 × 103 to 40 × 103 copies/m3 and 3.8 × 103 to 7.2 × 103 TCID50/m3), with aerosol size distributions that showed peaks in the region of particle size less than 1 μm; staff offices had peaks in the region of particle size greater than 4 μm.
Conclusions and Relevance
In this systematic review, the air close to and distant from patients with coronavirus disease 2019 was frequently contaminated with SARS-CoV-2 RNA; however, few of these samples contained viable viruses. High viral loads found in toilets and bathrooms, staff areas, and public hallways suggest that these areas should be carefully considered.
[link url="https://www.cidrap.umn.edu/news-perspective/2020/12/news-scan-dec-28-2020?"]CIDRAP material[/link]
[link url="https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774463"]JAMA Network Open study (Open Access)[/link]