#15,203
Ten days ago, in COVID-19: The Airborne Division, we looked at the sharp divide between advice being offered by the CDC and the World Health Organization on what constitutes `adequate' infection control measures (droplet vs. airborne) and PPEs for COVID-19.
This makes a huge practical difference, because the WHO - which subscribes to the `droplet' theory - only recommends `contact and droplet precautions' (gloves, gown, surgical mask & eye protection) for HCWs dealing with COVID-19 patients.
Many countries, perhaps most, are going by the WHO guidelines. But our own CDC has long recommended more stringent `Airborne' precautions (when PPE supplies permit) for HCWs dealing with COVID-19 cases (see graphic above).
As a practical matter, there aren't currently enough disposable N95 respirators to equip every doctor, nurse, of 1st responder, and I suppose some would argue that renders the debate between airborne and droplet moot.
But HCWs should at least know the risks they being asked to take, and if - as the following study suggests - a 2-meter rule of spatial distance is insufficient, the public, employers, and HCWs should know that as well.
As always, this isn't the definitive word on the subject, just a review of the literature and the conclusions made by the authors. Follow the link to read the full report.
Airborne or droplet precautions for health workers treating COVID-19?
Prateek Bahl, Con Doolan, Charitha de Silva, Abrar Ahmad Chughtai, Lydia Bourouiba, C Raina MacIntyre
The Journal of Infectious Diseases, jiaa189, https://doi.org/10.1093/infdis/jiaa189
Published: 16 April 2020 Article history
Abstract
Cases of COVID-19 have been reported in over 200 countries. Thousands of health workers have been infected and outbreaks have occurred in hospitals, aged care facilities and prisons. World Health Organization (WHO) has issued guidelines for contact and droplet precautions for Healthcare Workers (HCWs) caring for suspected COVID-19 patients, whilst the US Centre for Disease Control (CDC) has recommended airborne precautions.
The 1 – 2 m (≈3 – 6 ft) rule of spatial separation is central to droplet precautions and assumes large droplets do not travel further than 2 m (≈6 ft). We aimed to review the evidence for horizontal distance travelled by droplets and the guidelines issued by the World Health Organization (WHO), US Center for Diseases Control (CDC) and European Centre for Disease Prevention and Control (ECDC) on respiratory protection for COVID-19.
We found that the evidence base for current guidelines is sparse, and the available data do not support the 1 – 2 m (≈3 – 6 ft) rule of spatial separation. Of ten studies on horizontal droplet distance, eight showed droplets travel more than 2 m (≈6 ft), in some cases more than 8 meters (≈26 ft). Several studies of SARS-CoV-2 support aerosol transmission and one study documented virus at a distance of 4 meters (≈13 ft) from the patient.
Moreover, evidence suggests infections cannot neatly be separated into the dichotomy of droplet versus airborne transmission routes. Available studies also show that SARS-CoV-2 can be detected in the air, 3 hours after aeroslisation. The weight of combined evidence supports airborne precautions for the occupational health and safety of health workers treating patients with COVID-19.
Droplet Transmission, Respiratory Protection, Coronavirus, Mask, SARS-CoV-2, COVID-19You'll find some recent blogs on aerosol vs droplet transmission of COVID-19 below:
EID Journal: Aerosol and Surface Distribution of SARS-CoV-2 in Hospital Wards, Wuhan, China
Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 - NEJM
Is the coronavirus airborne? Experts can’t agree - Nature
Rapid Expert Consultation on the Possibility of Bioaerosol Spread of SARS-CoV-2 for the COVID-19 Pandemic (April 1, 2020) - Nat. Academy Sci.
