For the entire summer of 2020 I have been endorsing the idea of enjoying the weather and getting outside. It’s always been with the caveat that come fall we will have to make some compromises in the way we live to manage #COVID19. It really about not going nuclear.

We’ve learned a lot about infectivity of #SARS_CoV2 over the past 9m & have step wise instituted health policies that have been effectively mitigating risk. This process is a lot like building a plane while trying to fly it. Not surprisingly, we’ve all seen conflicting advice.

Infectivity just like combustion is a concentration dependent phenomena. That much lauded R value is dependent on separation and number of cases. An engine can not run if it cannot compress its fuel close enough to propagate combustion nor can a bomb explode.

And this is where conflicting views on airborn spread and ventilation requirements come to light, because all droplets can be aerosolized under the right conditions. Fortunately viral dose drops significantly with aerosolization and so does infectivity.

These changing guidelines are the result of repeated iterations of knowledge. Raw data translated into small trials, extrapolated into public health policy while larger trials happen. Epidemiologists chime in on real time numbers and and the plane is tweaked and modified.

This process is mostly normal, but the speed of its implementation is unprecedented. For the first time both professionals and novices have access to the data in real time. I particularly love watching the epidemiologists and infectious disease docs go at each other.