Although limited evidence is available, the results of this study suggest that healthcare workers directly exposed to COVID-19 should follow more aggressive protection measures, including the use of respirators (N95 masks) instead of the use of surgical masks.
Bahl, P. et al. Airborne or droplet precautions for health workers treating coronavirus disease 2019? The Journal of Infectious Diseases (2020). https://doi.org/10.1093/infdis/jiaa189
15 May 2020
Healthcare organizations that are faced with limited resources such as masks, face shields, gowns (personal protective equipment, or PPE) must make resource allocation decisions that both conserve limited resources and also adhere to best practices. The evidence so far regarding transmission of SARS-CoV-2 has suggested that it can be transmitted by droplets – that is, by talking, breathing, coughing or sneezing – which can travel up to two metres or six feet. As a result, healthcare workers have been provided PPE that aligns with droplet precautions. However, evidence related to COVID-19 is rapidly evolving. The authors of this study conducted a systematic review (a review of multiple papers exploring the same topic) for evidence of horizontal distance travelled by respiratory droplets to determine how far these droplets can travel. Several methodologies were used for the included studies and the authors recognize that horizontal distance of droplets depends on various factors, including droplet size. Nevertheless, eight of the ten studies discussed a horizontal trajectory greater than two metres. Studies that were based on modelling (rather than experimental tests) found that droplets could spread as far as eight metres. All but one of the studies that were experimental and using human subjects found more conservative estimates for droplet distance, up to three metres. The authors recommend that based on this evidence, healthcare workers treating patients with COVID-19 should adopt airborne precautions, which include stronger PPE requirements such as the use of N95 masks as opposed to surgical masks.
Summary by: Jennifer Gutberg