We need population testing to get an actual idea of how many people in an area have it. There's likely way more cases nationwide than being reported. In NYC, most asymptomatic/low symptom cases of coronavirus aren't going to be tested until antibody testing later on.
Also a good news actually.
For each disease we estimate a number called R0, which is how many people the average person will transmit it to if no precautions are taken.
Herd immunity sets in when only 1/R0 people have not managed to get it.
With the flu, R0 is about 1.3. Meaning that herd immunity to a particular strain starts slowing the spread after about 1/4 of us are immune. (It can continue spreading for some time after that point.) I calculated that from the fact that 1 - 1/1.3 = 0.23076923076923076...
R0 for COVID-19 is likely around 5.6 +- 0.9 per https://www.medrxiv.org/content/10.1101/2020.02.07.20021154v... we take the middle of that range, over 82% of us have to get it before herd immunity starts to work in our favor.
We got lucky last time around in Seattle area, in that it only cost us $1m and 0 deaths to get it under control.
If you look at the Italian data, their % positive level never crossed ~30%, and overall averaged <20%. That might indicate that susceptibility for this agent is well below 50%.
https://en.wikipedia.org/wiki/2020_coronavirus_pandemic_in_I...
The more likely explanation is that social distancing was implemented early enough, and tests were given to people who might or might not have had it.
There is no reason to believe that we burned through most of the vulnerable people in the population.
It is worth considering that even if the % immune is lower than the herd immunity level, it still slows the outbreak and reduces Re. That gives us a much slower ramp up and gives other measures like less restrictive social distancing, contact tracing, etc. a chance to work. Even if all those together only get Re down to between 1 and 2, we still benefit since it means we might only need another 1 or 2 lockdown periods before we get an effective vaccine.
there is a very strong age dependence with this disease, and probably many other risk factors - predisposition to pneumonia etc.
https://www.yahoo.com/news/teams-retrieving-280-bodies-day-1...
The increase is roughly in line with similar estimates from excess mortality [2], so I would guess they are catching most of the deaths with the new reporting scheme.
[1] https://www1.nyc.gov/assets/doh/downloads/pdf/imm/covid-19-d...
[2] https://www.nytimes.com/interactive/2020/04/10/upshot/corona...
having 10x more infections yet the situation is still manageable is actually pretty good news
Not really, they are testing a population of only young, healthy and fit individuals with an obesity rate and other conditions absolutely not in line with the general population.