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Old 03-28-2020, 01:37 AM
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DSeid is online now
Join Date: Sep 2001
Location: Chicago, IL
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Stranger - you seem to know more than the experts -

- Who do NOT believe that aerosols are a significant factor in transmission (mostly droplets).

- Who understand that a curve can be flattened by multiple means. Keeping those who use the resources the most if they get sick from getting sick, is a means of flattening the curve. The issue is that with the current sets of assumptions it would not flatten it enough, and we don't know enough to be able to say that those assumption are definitely not true. Theoretically if in Italy those uninfected over 70 were isolated early on and kept from catching the virus, Italy's curve would have been significantly flattened. Just not realistic to achieve the goal with that alone.

- Who understand that herd immunity is NOT something that only applies to endemic diseases and is a critical part of modeling the dynamics of every epidemic or pandemic. Local herd immunity is what broke the spread of Zika in Brazil, for example. Herd immunity is what happens under a flatten the curve scenario as well, just slowly and controlled enough to avoid overwhelming the healthcare system at its peak.

- Who understand that good confidence intervals do not require testing 5% of the population with decent random sampling techniques. In fact the WHO protocol for such studies (see section 4.1) discusses the 95% confidence intervals with just 100, 200, and 300 samples at different levels of true seroprevalence.

There is indeed a whole mess of misinformation going on. Claims that COVID-19 is primarily aerosol spread (other than only aerosol in very specific high risk circumstances), claims that herd immunity does not apply to it, claims that studies need 5% of a population to be valid ... lots of misinformation.

Given the information we don't yet know about COVID-19, and its current rate of rise, the only prudent course is to maintain "the hammer" right now. No question that arbitrary dates should not be how decisions of what to modify in the approach when are made, but additional information as it is learned, and the response of disease in our population to the interventions.

Nevertheless to THE HYPOTHETICAL that cmosdes posed - yes, experts (like Mark Lipsitch) believe that for this virus 50% of a population immune/resolved would be sufficient to achieve herd immunity and stop spread (go to 9:20 on, especially at the 10:55 mark). Lipsitch takes pain to point out that case fatality rate is not the same as infection fatality rate and that we simply do not know what the latter is. Note he offered other social distancing option than full hammer approach as possibly effective.

IF, theoretically but with some reason to believe, children functioned the same as those resolved, then the 21 to 27% (depending on if you want to define child as under 15 or under 19 yo) of NYC that are children, get you halfway there. IF, also theoretically but with some reason to believe, there are 8 asymptomatic to symptomatic ones, then herd immunity and flattening of the growth would occur when symptomatic (not confirmed) infections reached about 270,000. Which would be by three weeks later would have 2700 total deaths before the daily death rate started to slow down. Which would be in a week, and would correspond with ICU admissions slowing down within the next few days. Which of course might occur due to social distancing beginning two weeks ago as well.

If hypothetically children are actually equally as contagious as adults, and there are no asymptomatic cases ... well then herd immunity is a long long way off. Any flattening is exclusively because of the hammer approach in that case.

Reality is likely somewhere between the two. But none of us know.

A hundred or so New Yorkers in each decadal age cohort tested for serologies according to the WHO protocol would be able to at least give a broad answer to which of the two are closer to the truth, at least on the asymptomatic infection side.

Settimo, I'm not sure how to do the math you propose, but from a practical POV you are best off considering any individual outside your immediate household circle as if they were contagious and limit your time within their 6 foot circle and the frequency of those contacts as best you can. Along with washing your hands, etc.