It requires you wear the mask at all times. And that you change it regularly by removing folding inwards and disposing securely.
Otherwise you may pick up an infection and then put a mask on afterwards which necessarily means that much of the shedding caught in the mask will be breathed back in - From mouth to nose and vice versa.
Or put the mask back on backwards or wave it around in the air, put it on surfaces and the like.
All of which amplify the current infection you have making you more infectious when you take the mask off.
And may explain why at a local Covid secure school they all went down with the usual back to school viral cold far more rapidly this year than they normally do.
What we don’t know - because we’re not hamsters permanently in cages - is what the network effects are.
For all the talk about how much masks help, I haven't seen great studies that aren't in vitro, not specifically in health care settings, and not specifically around someone known to have it. I found this which is at least a natural experiment:
> Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1,1.4, 1.7, and 2.0 percentage points in 1–5, 6–10, 11–15, 16–20, and 21 or more days after state face mask orders were signed, respectively.
I'm trying to sort of if those percentages are absolute or relative. I think they're absolute because some of the graphs are labeled "percentage point change," but using absolute percentage point changes for an analysis like this is seriously flawed because a 2% reduction could range anywhere from a miracle to statistically significant, but negligible.
It's also not clear if people feel safer wearing face masks, so they engage in riskier activities.
My guess is they're not as effective as claimed because while the Bay Area has pretty high compliance, if masks were systemically very effective, we'd see case rates drop a lot faster, not still be above mid-June numbers. That said, whatever the Bay Area is doing right now is working.
It requires you wear the mask at all times. And that you change it regularly by removing folding inwards and disposing securely.
Otherwise you may pick up an infection and then put a mask on afterwards which necessarily means that much of the shedding caught in the mask will be breathed back in - From mouth to nose and vice versa.
Or put the mask back on backwards or wave it around in the air, put it on surfaces and the like.
All of which amplify the current infection you have making you more infectious when you take the mask off.
And may explain why at a local Covid secure school they all went down with the usual back to school viral cold far more rapidly this year than they normally do.
What we don’t know - because we’re not hamsters permanently in cages - is what the network effects are.