Friday, August 21, 2020

BMJ Editorial: Airborne Transmission of Covid-19

Photo Credit PHL (Public Health Image Library)


I suspect that a few years from now - when historians are able to take a dispassionate look back at the pandemic of 2020 - their biggest take-aways will be how often we underestimated this pandemic virus, and how slow we were to pivot when new evidence emerged.  

  • During January and well into February, most governments naively believed that China would somehow contain the novel coronavirus, even as it was already spreading silently on several continents. 
  • It would take until the second week of March before the World Health Organization would finally state that COVID-19 `could be characterized as a pandemic'.
  • Mild or moderate illnesses - which comprise the majority of infections, were assumed to be self-limiting, and people would fully recover after a week or two. Today, there is ample evidence that for many, prolonged illness and disability is a genuine concern (MMWR Report).

And nearly 8 months into COVID-19's world tour, the debate over whether SARS-COV-2 is spread via `airborne transmission' - and even the definition of what constitutes `airborne transmission' - is still raging.  

Six months ago many observers saw the rapid spread of the virus aboard the Diamond Princess cruise ship in Japan as suggestive of airborne spread (see CDC HAN #00430: Guidance about Global Travel on Cruise Ships), and a number of `super spreading' events in restaurants, churches, and other large gatherings have added to those suspicions.

MMWR: High COVID-19 Attack Rate Among Attendees at Events at a Church

MMWR Early Release: COVID-19 Superspreading Event In A Church Choir

Environmental studies have consistently found evidence of SARS-CoV-2 contamination in rooms occupied by infected patients (even asymptomatic cases), and often many yards away, either carried by air drafts or transferred by people and/or materials that had close contact with an infected person. 

EID Journal: Prolonged Infectivity of SARS-CoV-2 in Fomites

EID Journal: Persistence of SARS-CoV-2 in Aerosol Suspensions

EID Journal: Detection of SARS-CoV-2 on Surfaces in Quarantine Rooms

EID Journal: Aerosol and Surface Distribution of SARS-CoV-2 in Hospital Wards, Wuhan, China

Despite limited evidence, the CDC decided early on to err on the side of caution, and back in February, advised:
Ask such patients to wear a face mask as soon as they are identified. Conduct patient evaluation in a private room with the door closed, ideally an airborne infection isolation room, if available. Personnel entering the room should use standard precautions, contact precautions, and airborne precautions, and use eye protection (goggles or a face shield). 
Recently, they upped the ante even more, warning:
Below are changes to the guidance as of July 15, 2020:
  • Added language that protective eyewear (e.g., safety glasses, trauma glasses) with gaps between glasses and the face likely do not protect eyes from all splashes and sprays.

We've followed the research, and the debate over airborne spread closely for months, including: 

Scientists `Airborne' Letter To WHO & Another SARS-CoV-2 Ventilation Dispersal Study

EID Journal: Persistence of SARS-CoV-2 in Aerosol Suspensions

Meanwhile many public health agencies and organizations - including the World Health Organization - continue to issue less stringent `Droplet' guidance, pointing out that while there have been studies suggestive of `airborne' transmission, overall the evidence for that has been weak

All of which brings us to an editorial - published yesterday in the BMJ - which calls upon agencies and governments to `. . . acknowledge the evidence and take steps to protect the public'.

The authors don't maintain that the science is settled, only that there is enough evidence of airborne transmission to err on the side of caution, writing:
Urgent research is needed to better understand airborne transmission and measure viral aerosol outputs during respiratory activity and medical procedures. In the meantime, international guidance must acknowledge the weight of evidence supporting airborne transmission of covid-19 and include recommendations to promote effective preventive measures. How should infection control practice be changed if we provisionally accept that aerosols have an important role in viral transmission?
Follow the link to read:
Airborne transmission of covid-19
BMJ 2020; 370 doi: (Published 20 August 2020)
Cite this as: BMJ 2020;370:m3206
Nick Wilson, intensive care fellow, Stephen Corbett, director2, Euan Tovey, associate professor3
Correspondence to: N Wilson
Guidelines and governments must acknowledge the evidence and take steps to protect the public
          (Continue . . . )