[jjjensen90]

Because it's possible that there are many, many infected who don't seroconvert or ever manifest symptoms, and therefore would not have been tested with a PCR test, and would have a negative antibody test. We can see this in effect in studies of household attack rates and seroconversion. See this recent preprint and interesting thread (/r/covid19 is a strict science sub, not to be confused with /r/coronavirus) https://www.reddit.com/r/COVID19/comments/hdxwf5/intrafamili...

[arrrg]

But does this get us a lot?

In Brooklyn and Queens between 0.2 and 0.25 percent of the total population (!) died.

So this sort of puts a floor on the IFR and 0.2 is not that far off from the IFR determined through serological testing – maybe a half or a third of that.

So yeah, maybe there is an effect – but can it really be a drastic effect? I don’t think there are orders of magnitude of difference in there, maybe a difference of a few percent (e.g. an IFR of 0.45 instead of 0.5 percent)?

My working hypothesis has been an IFR of around 0.5% for a pretty long time, which seems pretty realistic to me.

[grey-area]

But looking at NYC now, after peaking in April, infections and deaths are way down and stabilised, in spite of rising infections in surrounding areas and very few travel restrictions. So something is going on that we don't understand, and it could have a significant impact.

If we have a higher immune population than we think, NYC might have passed the worst, if not millions will die in a second wave (though there are no signs of that yet). So this does matter.

[arrrg]

New York obviously “benefits” from an intensive first wave. Every additional infection makes spread harder for the virus.

As many European countries show (including Germany, where the infected population is very low, much lower than the European average, much much lower than Italy or Spain) it’s very possible to keep the epidemic at a low, simmering level without extremely drastic lockdowns.

Given a probably pretty low K value it’s also often sufficient to not be super-efficient about prevention. Some efficiency goes a long way.

[grey-area]

it’s very possible to keep the epidemic at a low, simmering level without extremely drastic lockdowns.

It's very hard to know the cause of the dramatic decline in nations that were hit hard, so I don't think we can attribute it as simply as that. It could be immunity we're unable to test (T-cell), weather meaning more are outdoors, awareness and measures like distancing and masks, or a mix of many things. We just don't know at this stage.

I'd note that Germany is still seeing outbreaks, and they were hit less hard in the initial wave in Europe. Italy in contrast, which has relaxed restrictions, is seeing very low levels of deaths and cases.

[jakeogh]

Excellent.

un-nerfed link: https://old.reddit.com/r/COVID19/comments/hdxwf5/intrafamili...

[jmull]

Well, this study estimates covid 19 by looking at survey data on influenza-like-illnesses. That means they were counting people who had flu-like symptoms.

Any potential people with covid19 but no symptoms would be above and beyond what’s being raised here.

[gvjddbnvdrbv]

Most of the people with flu like symtoms won't have had covid though.