Covid-19 Antibody Seroprevalence in Santa Clara County, California • Hacker News Board

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#21

Post by SpicyLemonZest » Fri, Apr 17, 2020, 4:36 PM UTC

zaroth wrote: post #11

makomk wrote: post #6

Earlier quoted context omitted.

Most signs so far suggest that the virus is basically uncontainable, short of everyone on the planet taking aggressive measures to stop it escaping China back in January or December.

That was back when China was claiming it didn’t transmit between humans, and ordering labs to destroy their samples. https://www.nationalreview.com/the-morning-jolt/chinas-devas...

Right, that's why people say the Chinese government's lies (and the WHO's acceptance of them) are at fault. The rest of the world certainly should have reacted sooner, ramping up PPE production and researching treatments and trying to slow it down. But the idea of complete containment, forming widespread green zones where the virus is not merely suppressed but eradicated, probably became impossible as early as February. (Some island or basically-island countries appear to be making it work, but it's not clear what their long-term plan is - are they just going to enact sakoku for the next 18 months?)

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#22

Post by beamatronic » Fri, Apr 17, 2020, 4:38 PM UTC

“These prevalence estimates represent a range between 48,000 and 81,000 people infected in Santa Clara County by early April, 50-85-fold more than the number of confirmed cases. Conclusions The population prevalence of SARS-CoV-2 antibodies in Santa Clara County implies that the infection is much more widespread than indicated by the number of confirmed cases.”

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#23

Post by ortusdux » Fri, Apr 17, 2020, 4:38 PM UTC

h2odragon wrote: post #3

I think the numbers will coma out to show this ripped through the USA in February; we slammed the barn doors closed well after the horse was gone. Of course that's not the narrative that fits agendas so just like with "why cant we test people?" back then, there will be many official reasons not to look for antibody data and to doubt what data gets gathered.

I keep hearing this sentiment, but I cannot square it with the fact that a non-trivial percent of infected people need to be on ventilators for roughly 20 days. If, back in December, 10k people had what we now know as Covid, there would have been dozens of people on ventilators for weeks at a time in January. The average flu patient needing intubation is only on a ventilator for about 5 days. I just don't see a situation where we have dozens of people testing negative for the flu yet requiring a higher level of ICU care and no alarm bells are raised.

My optimistic side wants the truth to be that there are many strains, and the worst one spread in the last few months. This would mean that there are other strains that provide adequate anti-bodies and yet are mild enough to go unnoticed by professionals.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#24

Post by slg » Fri, Apr 17, 2020, 4:39 PM UTC

pwned1 wrote: post #5

h2odragon wrote: post #3

I think the numbers will coma out to show this ripped through the USA in February; we slammed the barn doors closed well after the horse was gone. Of course that's not the narrative that fits agendas so just like with "why cant we test people?" back then, there will be many official reasons not to look for antibody data and to doubt what data gets gathered.

Based on the difference between CA and NY, I'd be willing to bet that it got here earlier, maybe in December.

California has 2X the population of New York. NY has more than 17X the number of deaths and while the daily deaths rate there is slowing it still far outpaces CA's daily rate. I don't know how you can look at those numbers and conclude the disease was spreading unchecked in California for multiple months.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#25

Post by [deleted] » Fri, Apr 17, 2020, 4:42 PM UTC

h2odragon wrote: post #3

I think the numbers will coma out to show this ripped through the USA in February; we slammed the barn doors closed well after the horse was gone. Of course that's not the narrative that fits agendas so just like with "why cant we test people?" back then, there will be many official reasons not to look for antibody data and to doubt what data gets gathered.

[deleted]

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#26

Post by tshadley » Fri, Apr 17, 2020, 4:44 PM UTC

gryson wrote: post #18

"We recruited participants by placing targeted advertisements on Facebook aimed at residents of Santa Clara County..." I wonder if these ads mentioned the purpose of the study, or if that information was only given out after initial contact (I don't know enough about IRB requirements here). A concern is that this could cause a selection bias for people who suspected they had the virus. People may respond to such an a…

Why would this matter as long as they got a good geographical sampling?

"We used Facebook to quickly reach a large number of county residents and because it allows for granular targeting by zip code and sociodemographic characteristics. We used a combination of two targeting strategies: ads aimed at a representative population of the county by zip code, and specially targeted ads to balance our sample for under-represented zip codes. In addition, we capped registrations from overrepresented areas."

Update: Okay, "Other biases, such as bias favoring individuals in good health capable of attending our testing sites, or bias favoring those with prior COVID-like illnesses seeking antibody confirmation are also possible."

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#27

Post by CubsFan1060 » Fri, Apr 17, 2020, 4:47 PM UTC

ortusdux wrote: post #23

h2odragon wrote: post #3

I think the numbers will coma out to show this ripped through the USA in February; we slammed the barn doors closed well after the horse was gone. Of course that's not the narrative that fits agendas so just like with "why cant we test people?" back then, there will be many official reasons not to look for antibody data and to doubt what data gets gathered.

I keep hearing this sentiment, but I cannot square it with the fact that a non-trivial percent of infected people need to be on ventilators for roughly 20 days. If, back in December, 10k people had what we now know as Covid, there would have been dozens of people on ventilators for weeks at a time in January. The average flu patient needing intubation is only on a ventilator for about 5 days. I just don't see a situa…

"a non-trivial perfect of known infected people"

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#28

Post by eightysixfour » Fri, Apr 17, 2020, 4:49 PM UTC

CubsFan1060 wrote: post #13

DennisP wrote: post #9

The problem with every one of these studies I've seen is that they come up with around 3% of the population having antibodies, while a typical false-positive rate for these tests is also around 3%. In this case they claim they adjust for the specificity (basically false-positive rate), but I didn't see that they reported what the specificity was. If the mortality really is very low, then it should be easy to prove. J…

This is certainly not a study. And certainly shouldn't be taken as good data of any kind, but it is interesting: https://www.livescience.com/coronavirus-in-pregnant-woman-hi... Sure as hell isn't random (all pregnant women... so all women for one. All at the same hospital is another). "Between March 22 and April 4, those hospitals screened 215 pregnant women for SARS-CoV-2 (the virus that causes COVID-19), and 33 wom…

Anyone know if there's been a follow-up to see if the women eventually developed symptoms?

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#29

Post by rumanator » Fri, Apr 17, 2020, 4:50 PM UTC

standardUser wrote: post #19

Add this to growing pile of evidence that this coronavirus is more widespread than most testing to date would suggest. How much more widespread still appears very unclear. There is a major ramping up of antibody testing happening right now, and multiple new tests being introduced, so we should have a better idea very soon. But the takeaway should be that this is a good thing. Every unknown case we uncover decreases t…

I don't follow your argument. If the epidemic is more widespread than initially thought, why do you assume that the effective transmission rate would potentially decrease? If anything, the transmission rate was higher than assumed and, due to the higher number of infections and how they spread exponentially,it would only ramp up.

And additionally, there are reports of reinfections among covid19 patients who were found to be cured.

Re: Covid-19 Antibody Seroprevalence in Santa Clara County, California

#30

Post by not2b » Fri, Apr 17, 2020, 4:50 PM UTC

gryson wrote: post #18

"We recruited participants by placing targeted advertisements on Facebook aimed at residents of Santa Clara County..." I wonder if these ads mentioned the purpose of the study, or if that information was only given out after initial contact (I don't know enough about IRB requirements here). A concern is that this could cause a selection bias for people who suspected they had the virus. People may respond to such an a…

Yes, the ads accurately described the study. Several friends of mine participated (I live in Santa Clara County).

Of course there is selection bias, which is why they make adjustments to make the sample better represent the population (see the abstract for details on this, or read the paper for all the details, there's well-established science behind these adjustments and it's up to the reviewers to be sure that they did it correctly). The point is that "they only found 50" is quite a large number compared to the number of confirmed cases.