Thread by @sciencescanner

I do think healthcare professionals need to be particularly careful. It seems clear that severe symptoms result from high viral load. If the virus gets to very high copy number before your adaptive immune response kicks in you are at very high risk if ARDS

1/n

If you are healthy & immunocompetant, then a major determinant of the outcome if that race will be initial exposure. If I am infected by 1cparticle, it takes 10 doubling times to get to 1000 particles - if I’m infected by 1000 particles simultaneously I’m there in zero time

2/n

So the higher the initial infectious load the shorter the time to any given threshold if viral load - and if that makes it shorter than the time taken to mount the immune response then severe symptoms result

3/n

Such a simple factor may very well underlie much of the variability in symptom severity between individuals - particularly because experience shows us that young, healthy doctors seem disproportionately likely to get “unexpectedly” severe symptoms

4/n

This has practical implications: it emphasises the hygiene element to the response. Makes it more likely that even if you get it, it will be a lower dose with proportionately milder symptoms

5/n

And raises the question of whether we should start giving front-line healthcare staff hydroxychloroquine prophylaxis now. HQX is pretty safe generally, and the data available suggests it results in milder cases of #COVID19 so even without RCT data the risk is low

6/n

If time to threshold viral load is the main driver of severe symptoms as I’m hypothesising, then attenuation of symptoms with something that reduces viral expansion is exactly what you’d expect, supporting the entire concept

7/n

Right now I can’t think of a single reason NOT to do it today. It’s a cheap, low risk intervention that could save thousands. And the best counter-argument I can find is that we haven’t yet PROVED it would help

8/8