. @UniofOxford prof Deborah Cameron notesa key respect in which small group teaching is a greater Covid risk than large lectures, casting doubt on @Cambridge_Uni's moving large lectures online while keeping small group teaching in person. ( @AlistairJarvis @michelledonelan) 1/

I'm devoting a single thread to her comments (originally posted on Facebook & reposted on Twitter with her permission), since I do not think their significance has yet fully registered with higher education, government & public health officials. 2/

To drive home their significance, I first draw attention to thispassage in (linked) US @CDCgov guidance for higher education:
"COVID-19 is mostly spread by respiratory droplets released when people TALK, cough, or sneeze" (my emphasis). 3/
https://www.cdc.gov/coronavirus/2019-ncov/community/colleges-universities/considerations.html

On the CDC's (linked) "How COVID-19 Spreads" webpage, talking is also listed alongside coughing and sneezing, in the second of four bullet-pointed means by which the virus "mainly" spreads. 4/
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html

Why does the CDC group something as apparently innocuous as talking together with coughing & sneezing as a significant risk factor? 5/

Because of mounting evidence, via case studies (some w detailed CDC analysis), that talking (or singing) was the most likely means by which Covid-19 was spread from a single individual to many others indoors, more than 2 meters away, via inhalation into their lungs. 6/

See this linked analysisof case studies by @Erinbromage, a Comparative Immunologist and Professor of Biology. 7/
https://www.erinbromage.com/post/the-risks-know-them-avoid-them

See also this survey of 58 case studies of "superspreader events" (SSE) by @jonkay, in which he draws attention to the dog that didn't bark. 8/
https://quillette.com/2020/04/23/covid-19-superspreader-events-in-28-countries-critical-patterns-and-lessons/

is of special relevance to this thread, since a large lecture, generally involving a single speaking individual, at some distance from the audience, is akin to @jonkay's red-underlined events that are absent from the list of SSEs. 9/

In addition to noting this fact in 1/, Deborah Cameron also draws attention to the respects in which small, participatory group teaching shares the risk factors of various catalogued SSEs. 10/

Why, then, are universities such as @Cambridge_Uni moving apparently less risky events online (large lectures), & trying to keep the apparently more risky events in person (small group teaching)? 11/