A review of currently available evidence of air contamination with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) found that while samples taken both near to and far from hospitalized patients contained SARS-CoV-2 RNA, the viral loads were low. The results of this review, published in JAMA Network Open, indicated that there was high viral loads present in areas such as bathrooms, staff areas, and hallways.
Across the 24 cross-sectional observational studies included, 893 samples were taken. Of these samples, 471 (52.7%) were in close-patient environments, 237 (26.5%) were in clinical areas, 122 (13.7%) in staff areas, 42 (4.7%) in public areas, and 21 (2.4%) in bathrooms. In close-patient areas, 82 samples (17.4%) were positive.
The data did not show any differences in results depending on the distance from patients in which the samples were collected (≤1 m vs >1-5 m; P = .22). There was a significant difference in positive air samples coming from intensive care unit (ICU) vs non-ICU rooms (25.2% vs 10.7%; P <.001). In rooms with negative pressure, the air positivity rate was 47 of 360 (13.1%) and in rooms with natural air or mechanical ventilation, the positivity rate was 6 of 66 (9.1%). Among the 21 samples from bathrooms, 5 (23.8%) were positive.
The overall positivity rate in clinical areas was 8.4% (20 of 237), which varied from 0 of 64 in anterooms to 6 of 22 at workstations (P <.001). For staff areas, 5 of 122 (12.3%) overall samples were positive, which varied from 5 of 26 in staff meeting rooms, 2 of 51 in changing rooms, and 8 of 45 in other types of staff rooms (P =.06). In total, 14 of 42 samples (33.3%) in public areas were positive, which varied from 9 of 16 in hallways, 2 of 18 in other indoor areas, and 3 of 8 in outdoor public areas (P =.01).
Overall, 81 viral cultures were performed across 3 studies. Of these, 13 (16.0%) were from clinical areas, 4 (4.9%) from staff areas, and 15 (18.5%) from public areas. In studies that performed quantitative reverse transcription polymerase chain reaction, the median RNA concentrations varied from 1.0 x 103 copies/m3 (interquartile range [IQR], 0.4-3.1 x 103 copies/m3) in clinical areas to 9.7 x 103 copies/m3 (IQR, 5.1-14.3 x 103 copies/m3) in bathrooms.
Protective equipment removal and patient rooms had high concentrations per titer of SARS-CoV-2. In 2 patient rooms, results found RNA concentrations of 2.0 x 103 copies/m3 for particles greater than 4 μm, and 1.3 x 103 copies/m3 for particles sized 1 to 4 μm. Study authors also found 927 and 916 copies/m3 of those sizes in each room, respectively. In 2 protective equipment removal rooms, concentrations varied between 12.0 x 103 and 40.0 x 103 copies/m3 for particles less than 1 μm, and 2.0 x 103 to 8.0 x 103 copies/m3 for particles sized 1 to 4 μm.
Across the studies, context such as location, ventilation, distance and clinical context were infrequently detailed and misclassifications of variables categorized without sufficient detail may have occurred. The review was also limited by high variability of sampling and microbiology methods across studies. Surface contamination was not included in the analysis and several of the studies were not validated by peer review.
Investigators concluded that while the air around SARS-CoV-2 patients was frequently contaminated, this was rarely with viable virus. The data also suggest that the virus requires specific conditions to be transmitted via air and supports the effectiveness of surgical face masks in most circumstances, said investigators. They also highlighted that the high viral loads found in some areas, such as bathrooms, staff areas, and public hallways, suggest a need for careful considerations regarding these locations.
Birgand G, Peiffer-Smadja N, Fournier S, Kerneis S, Lescure FX, Lucet JC. Assessment of air contamination by SARS-CoV-2 in hospital settings. JAMA Netw Open. 2020;3(12):e2033232. doi:10.1001/jamanetworkopen.2020.33232.