To all:
I think I am well -qualified to address this issue based on more than 60 years of experience as an Inhalation Toxicologist, Aerosol Scientist and Risk Analyst and membership in National Academy of Medicine and election as an American Thoracic Society Fellow.
The answer is an emphatic --- Do not do it! , irrespective of what you call it, a class, a course, a practice. My views are emphatic for indoor performances and only slightly less emphatic for out door gatherings.
A real world example occurred in the Skagit Valley of Washington State in early March (? )when a choir practiced for several hours and many were infected as a result of one or two infected members.
Because of poor communications between scientists in different disciplines we spent months not acknowledging droplets are aerosols. The technical definition of an aerosol is -- a relatively stable suspension of solid particles and /or droplets in a gaseous media.
Yes, virus particles exhaled in droplets are aerosols and the aerosol particles follow the laws of physics as the particles are dispersed. The six foot rule is only a CRUDE index of exposure. Have your students calculate the virus load in a room of various dimensions with an assumed source and no ventilation, 1 or 5 or 10 air changes an hour. Do a similar exercise for a one hour staff meeting and have the Department Chair seated in different locations relative to the air inlet and air outlet. Ventilation is important.
I have had some up close experience on these issues when I learned a week after visiting my cardiologist that he was infected and in the ICU with Covid-19. Fortunately, I have had no symptoms. However, yesterday after battling red tape for 3 days I had a blood draw to test for presence or absence of virus antibodies. It is useful to keep in mind that 40% of infected individuals are asymptomatic , a great opportunity for spread of virus by asymptomatic carriers.
My colleagues at the Lovelace Institute have Biological Safety Class 3 facilities so they can work with nasty viruses. A few years ago they purposefully infected ferrets with a new influenza virus and the moved air through that cage to an adjacent cage with naive ferrets. No surprise, those down wind ferrets came down with influenza. Yes, ferrets and people respond in a similar fashion to these novel viruses.
STAY AWAY FROM INFECTED INDIVIDUALS AND WEAR A MASK.
Roger McClellan
