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Comment by cwhiz | Hacker News Reader

Back of the envelope they are estimating a little under 2 undiagnosed cases for every confirmed case. Putting our “actual” total around 42 million as of today.

I have no reason to doubt this particular study but I’ve seen other studies estimating up to 10x actual for every confirmed. It seems there is no great way to know this without some consistent, nationwide, antibody testing effort. Which hasn’t happened and by now may be too late to ever happen.

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Even antibody tests can underestimate the number of infections as the levels can drop below the detection threshold in some patients after several months. This effect will become more pronounced the longer the pandemic continues. In order to get really accurate data on infections we have to repeatedly test the same subjects, like in the UK's REACT study.

https://www.imperial.ac.uk/medicine/research-and-impact/grou...

Or alternatively test for T cell response. But that's a more complex and expensive assay.

The fraction of infections which are diagnosed varies quite a bit by circumstance, e.g. available test capacity. In general I get the impression that 10x was typical early on and 3x may be more typical now.

https://www.acpjournals.org/doi/10.7326/M20-3012

Metanalysis mostly based on data from the first spike.

Looks like about 50% of cases are asymptomatic in the general population, with a higher proportion of asymptomatic cases in younger populations?

Remember that not everyone with symptoms is going to bother getting tested. In fact, everyone I know who has had possible COVID symptoms in the past few months hasn't bothered to get tested.

On some level I don't really know why you would get tested, except if you're curious. I'm a person in my 30s. If I got covid symptoms, I would warn everyone I've had close or transitive close contact with -- that is, our nanny, my son's tutor, and my son's classroom. But I don't know if I would bother to get tested. How does knowing you have it help? I guess if I was sure I had it it would be nice to get confirmation so that I could have a strong belief I'm immune going forward. But other than that I'm not sure how it helps.

It helps because some of those people you are warning have jobs with actual consequences if infection, or live with people that do. Like your sons teachers.

You go get tested so you can tell them “false alarm it’s all good”.

no you can't, and that is part of the problem. even if you test negative, the test isn't 100% and you still have to ask as if you have it

Right that's my understanding. I guess this is a good reason to consider getting tested though.

It can help if you get results quickly enough. And if you trust the results. If I came into close contact with someone who tested positive I wouldn't trust a negative test. If I had no symptoms I'd quarantine for 10-14 days. For people with tertiary exposure, through me, I have no idea how they should handle it.

I was severely ill with upper-respiratory symptoms about a month ago. Knowing if I had covid was critical information. If I had covid, going to a hospital or clinic for help was safer (for me) I can't catch covid twice. If I didn't have covid, I was already sick and getting covid on top of that would be a serious danger to my life.

I got close to needing to go to the hospital but decided not to. Turns out that was a good idea, I didn't have covid (PRC test).

It feels like the more aggressive the estimate is for the upper bound the less accurate it sounds, whether that's true or not. Somehow it just feels more believable that it's 2x instead of 10x without considering evidence either way. I think epidemiology is a tough field because you never actually have any verifiable ground truth.

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