With the acknowledgement that airborne transmission of COVID-19 can occur in crowded and closed environments, there is concern that the virus could easily spread within a hospital, leading to a serious outbreak.
Early evidence from China, together with other studies, has suggested that COVID-19 could be easily transmitted through the air. With an increasing number of patients admitted to hospital with the virus, a team from the UK and France sought to examine all the available published evidence on air contamination surrounding patients and healthcare professionals in hospitals. The team searched all the major databases from January 2020 to the end of October 2020, including preprint articles on the servers BioRxiv and MedRxiv, as well as checking the reference list of identified articles. Information on the setting, ventilation system, number of air samplings performed, sampling methods and positivity rates were extracted. Furthermore, the data were classed in terms of the area examined e.g., close patient environments, toilets/bathrooms, clinical areas, staff areas and public areas including hallways and indoor or outdoor areas. The authors also looked for data on viral loads and viral culture results.
From initially finding 2284 articles, after screening of the abstracts and removal of duplicates, 24 were included in the analysis. All of the articles reported testing for COVID-19 using PCR and were cross-sectional observational studies. A total of 893 air samples were collected across the 24 studies including 52.7% (471) from close patient environments, 26.5% (237) from clinical areas (including 107 from intensive care units), 13.7% (122) from staff areas with the remainder collected from public areas and toilets and/or bathrooms. When looking at the positivity rates, only 17.4% of the air samples from patient areas tested positive for COVID-19. In clinical areas, the positivity rate was 25.2% from the 107 intensive care units which was higher than from non-intensive care areas (10.7%). In rooms with negative pressure, the positivity rate was 13.1% and the overall positivity rate for clinical areas was 8.4%. Interestingly, the positivity rate was 23.8% from toilets and or bathrooms. A recognised limitation of the study was the absence of testing for surface contamination. Commenting on these findings, the authors noted that while many areas appeared to be contaminated with COVID-19, the actual levels of viable virus were actually very low.
Birgand G et al. Assessment of air contamination by SARS-CoV-2 in hospital settings. JAMA Netw Open 2020 doi:10.1001/jamanetworkopen.2020.33232