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Covid-19 at a homeless shelter in Boston: Implications for universal testing

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Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#101

Post by smsm42 »

jlmorton wrote: post #14
jcp2fa wrote: post #6

> Cough (7.5%), shortness of breath (1.4%), and fever (0.7%) were all uncommon among COVID-positive individuals It seems the more important point here is that the majority of the COVID-positive individuals were asymptomatic, putting another datapoint towards the conclusion that there are orders of magnitude more people that have this disease than have tested positive. We need more studies to gather data on these asym…

We already have lots of data that says this is not true. For instance, on the Diamond Princess, widespread testing of a confined group initially found many asymptomatic infections, but the majority of those turned out to be pre-symptomatic, not asymptomatic. Longer term follow-up found ~25% of infections were asymptomatic. In the US, we're now doing significant amounts of testing, but we're still primarily testing on…

What's "significant amount of testing"? In Santa Clara country, for example, 16585 tests have been done[1], that's less than 1% of the population. I know from personal experience of several people that it's next to impossible to get tested if you don't have very severe symptoms. Positivity rate is 10.8% - over people which are sick enough to get tested.

> Given a seeding of cases in mid-to-late January, even without social distancing measures, it would be unlikely to have 10% of the population infected yet

This sounds like circular logic - how we know it indeed started in January and not before? How do we know how many had it asymptomatically if we didn't test 99% of the population? We're making assumption based on knowledge gathered by select sample of 1% chosen by severity of symptoms - how can we make conclusion about how it works in the rest of the population and what's the dynamics there?

[1] https://www.sccgov.org/sites/covid19/Pages/dashboard.aspx

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#102

Post by DenisM »

arcticfox wrote: post #70
duxup wrote: post #43

Earlier quoted context omitted.

Jebus, 9% false positive ... is that even useful?

I mean, it's not great, but imagine if it was so cheap and fast we could test the entire population on a consistent basis. In a hypothetical scenario of 1% of the population actually having COVID and 9% testing false positive, you could ask all 10 positive results to self-quarantine and that'd probably be a pretty effective way of shutting down the virus without asking the whole population to stay home. Once the viru…

You need to also take into account the false positive too (1% iirc). Under your priors a group of 100,000 people will have 1000 infected and 99,000 not infected. Specifically:

99,0000.09 = 8,910 false positives 99,0000.91 = 90,090 true negatives 1,0000.99 = 990 true positive 1,0000.01 = 10 false negative

So going through your plan will isolate 8,910 + 990 = 9900 people (9.9% of the population), catching 990 actual cases and letting loose 10 cases.

In other words we can isolate 10% of the population and reduce the number of carriers by 990:10 ratio. This seems more effective than the current 100% isolation. All we need is the tests now.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#103

Post by duxup »

DenisM wrote: post #94
duxup wrote: post #43

Earlier quoted context omitted.

Jebus, 9% false positive ... is that even useful?

Great question, and the one I struggled with a lot. When I finally saw the light it was like find the glasses I have misplaced three days ago. Here: 1. Efficacy of a test can only be judged against specific priors, not any possible circumstance. 2. Likewise, the goal of a test is to assist in making a particular decision, not all possible decisions. Specifically 9% false positive rate is not useful for testing genera…

Thank you, yeah at large scale I could see how that might help.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#105

Post by RandallBrown »

kens wrote: post #34

Regarding the title "Covid+", it seems that most people (even on the news) don't care about the difference between SARS-CoV-2 (the virus) and COVID-19 (the disease). Is this distinction being abandoned? (I'm not trying to be pedantic here; I'm just curious about the common usage.)

SARS-CoV-2 vs. COVID-19 vs. Coronavirus vs. Covid

Doesn't matter for nearly 100% of my daily discussion about the pandemic.

I typically say Coronavirus or sometimes covid because it's faster to say or type.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#106

Post by tomerico »

Alex3917 wrote: post #63
jcp2fa wrote: post #6

> Cough (7.5%), shortness of breath (1.4%), and fever (0.7%) were all uncommon among COVID-positive individuals It seems the more important point here is that the majority of the COVID-positive individuals were asymptomatic, putting another datapoint towards the conclusion that there are orders of magnitude more people that have this disease than have tested positive. We need more studies to gather data on these asym…

> Imagine if 10+% of the population already had COVID and where immune By some estimates we need over 80% of the population to get it in order to achieve herd immunity, so if only 10% of the population has it we're not very close at all to this being over.

The first 10% to be infected, are also likely to be the highest spreaders (people in close contact with a high amount of strangers). The effect should hopefully be higher than 10% reduction in the reproduction rate.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#107

Post by zzzzzzzza »

usaar333 wrote: post #75
MiguelVieira wrote: post #55

Earlier quoted context omitted.

Likewise, South Korea reports a fatality rate of about 2% https://www.worldometers.info/coronavirus/country/south-kore... Since they have coronavirus relatively under control and have been doing extensive testing and contact tracing for months, it's plausible that they've caught most cases. It's wishful thinking to believe the infection fatality rate is an order of magnitude lower.

It is not plausible they caught most cases. Here's the result of randomized testing in Iceland, which also has the virus under control and has done even more testing per capita ( https://www.nejm.org/doi/full/10.1056/NEJMoa2006100?query=fe... ) Randomized testing was still finding 0.6% of the population (outside those otherwise quarantined already) actively infected. This means even in Iceland, less than half of infe…

But you just ignored the evidence from the diamond princess?

and meanwhile germany's data points toward a similar conclusion as the south korean data

singapore also has a 1.5% deaths/recovered... and it's been higher in the past if you've been following closely (as high as 2%... question is where have all the new cases been coming from?)

icelands data could easily be skewed if they avoided a nursing home getting infected, given their low number of cases, and even there 1% fatality seems plausible.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#108

Post by Daishiman »

pm_me_ur_fullz wrote: post #9
easytiger wrote: post #5

Earlier quoted context omitted.

Yup. And for far longer.

I really don't understand why people immediately want to discredit the idea that US patient zero was not the first in US. Or that this virus was around earlier and that there are limitations in contact tracing capabilities. This seems to have the toughest aspect of gaining consensus. Need antibody tests now, and ones that work reliably.

This hypothesis has already been tested by Stanford and found to be false.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#109

Post by notJim »

cgb223 wrote: post #52
jlmorton wrote: post #14

Earlier quoted context omitted.

We already have lots of data that says this is not true. For instance, on the Diamond Princess, widespread testing of a confined group initially found many asymptomatic infections, but the majority of those turned out to be pre-symptomatic, not asymptomatic. Longer term follow-up found ~25% of infections were asymptomatic. In the US, we're now doing significant amounts of testing, but we're still primarily testing on…

> In the US, we're now doing significant amounts of testing, but we're still primarily testing only those with severe symptoms Its not a significant amount of testing if we're only testing those with severe symptoms Here in SF at least there are scores of people I know who all were sick with a "weird flu" at some point from February to now who would all kill for a test to show that they have COVID immunity. These are…

> These are people who could potentially go back into society

Do we know this for sure? I've read that we're seeing re-infections of people who previously had it, but it wasn't clear exactly what was happening.

Re: Covid-19 at a homeless shelter in Boston: Implications for universal testing

#110

Post by dang »

zadkey wrote: post #2

(Regarding the Headline) Surely you mean 35% of homeless who were tested. We can't say for certain that the sample is an exact representation of the general population of the homeless in Boston. "Upon observing a cluster of COVID-19 cases from a single large homeless shelter in Boston, Boston Health Care for the Homeless Program conducted symptom assessments and polymerase chain reaction (PCR) testing for SARS-CoV-2…

We've changed the title in accordance with the site guidelines.

Submitted title was 'Boston study finds 35% of homeless are Covid+ (via PCR)'

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