Hospital air frequently contaminated with SARS-CoV-2, though
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Around 17% of air samples taken close to patients hospitalized with COVID-19 were contaminated with SARS-CoV-2 RNA, although the viruses were rarely viable, according to findings from a systematic review published in JAMA.

Controversy remains regarding the transmission routes of SARS-CoV-2. The objective was 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.

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. 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.

-- 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.

-- There was no difference according to the distance from patients.

-- 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 SARS-CoV-2 RNA concentrations varied from 1.0?×?103 copies/m3 in clinical areas to 9.7×103 copies/m3 in the air of toilets or bathrooms.

-- Protective equipment removal and patient rooms had high concentrations per titer of SARS-CoV-2, 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.

Conclusively, in this systematic review, the air close to and distant from patients with COVID-19 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.