Superspreading events (one study: 20% of cases) - Printable Version
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Superspreading events (one study: 20% of cases) - M T - 08-22-2020
This study in Georgia sheds some light on the so-called superspreading events. (distinguished from superspreaders; as I understand it, Mardi Gras might be a superspreading event)
The study finds that 2% of the cases appear to cause 20% of the new infections. (and, I would expect, conversely, 98% of the cases cause 80% of the new infections). (Btw, notice that statement is not about superspreading events, but superspreaders.)
Characterizing superspreading events and age-specific infectiousness of SARS-CoV-2 transmission in Georgia, USA
I've not gotten through this yet, so maybe I'll have more to say. It does have information about R before and after shelter-in-place.
IMO, superspreading at events is more about policy (allowing the events) and individual behavior (cautious vs it-doesn't-exist and everything in between), than about the disease itself.
RE: Superspreading events (one study: 20% of cases) - fullmetal - 08-22-2020
It makes sense that those who slack on precautions would end up getting the disease...and that they would socialize with other like-minded people who don't take precautions seriously. (Not entirely sure that victims of a superspreading event are all necessarily cavalier about precautions, but I haven't seen data one way or the other.)
Tangent: The Sturgis motorcycle rally concluded recently. People are now looking for evidence of virus transmission and spread secondary to the event...there have been some, but the real question is if the infections are happening at a rate higher than that of background community spread. Being a motorcycle event, a lot of it was outside, but also being a party, there was a lot of indoor activity as well.
RE: Superspreading events (one study: 20% of cases) - BostonCard - 09-02-2020
(08-22-2020, 02:40 PM)fullmetal Wrote: Tangent: The Sturgis motorcycle rally concluded recently. People are now looking for evidence of virus transmission and spread secondary to the event...there have been some, but the real question is if the infections are happening at a rate higher than that of background community spread. Being a motorcycle event, a lot of it was outside, but also being a party, there was a lot of indoor activity as well.
The first death linked to Sturgis has been reported:
https://www.washingtonpost.com/health/2020/09/02/sturgis-rally-death-coronavirus/
The article notes that the event has been tied to 260 cases in 11 states, though if 400,000 attended, that does not seem like a disproportionate number.
BC
RE: Superspreading events (one study: 20% of cases) - fullmetal - 09-08-2020
Fox News reports that 19% of all new US covid cases discovered between Aug. 2nd and Sept. 2nd can be traced back to the Sturgis motorcycle rally. Oddly enough, the headline reads 20% while the article text says 19%...go figure.
Quote:"We conclude that the Sturgis Motorcycle Rally generated public health costs of approximately $12.2 billion," the researchers wrote in a paper. "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend."https://www.foxnews.com/health/sturgis-motorcycle-rally-coronavirus-cases-south-dakota
At least one self-described pro-Trump news aggregator site (okay, it looks exactly like the fake news clickbait sites of 2015-2016) published an opinion that cited 196 cases as of Aug. 28th (article published Sept. 2nd). Naturally, this was shared with me by one of my acquaintances on Facebook with...extreme views.
But...Fox News! Note that they're reporting the same paper and figures that other less controversial news sites are reporting...and these figures are not charitable toward the idea that Sturgis covid fears were overblown.
RE: Superspreading events (one study: 20% of cases) - 82 Card - 09-09-2020
(09-08-2020, 01:33 PM)fullmetal Wrote: Fox News reports that 19% of all new US covid cases discovered between Aug. 2nd and Sept. 2nd can be traced back to the Sturgis motorcycle rally. Oddly enough, the headline reads 20% while the article text says 19%...go figure.
Quote:"We conclude that the Sturgis Motorcycle Rally generated public health costs of approximately $12.2 billion," the researchers wrote in a paper. "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend."https://www.foxnews.com/health/sturgis-motorcycle-rally-coronavirus-cases-south-dakota
At least one self-described pro-Trump news aggregator site (okay, it looks exactly like the fake news clickbait sites of 2015-2016) published an opinion that cited 196 cases as of Aug. 28th (article published Sept. 2nd). Naturally, this was shared with me by one of my acquaintances on Facebook with...extreme views.
But...Fox News! Note that they're reporting the same paper and figures that other less controversial news sites are reporting...and these figures are not charitable toward the idea that Sturgis covid fears were overblown.
This paper appears to have been published simultaneously by the Center for Health Economics and Policy Studies at San Diego State. (Direct link to PDF download) The SDSU version includes a note: "Dr. Sabia acknowledges support from the Center for Health Economics & Policy Studies at San Diego State University, including grant funding from the Troesh Family Foundation and the Charles Koch Foundation...." This may explain why Fox News was comfortable reporting the findings.
lex24 - lex24 - 09-09-2020
(09-09-2020, 12:09 AM)82 Card Wrote:(09-08-2020, 01:33 PM)fullmetal Wrote: Fox News reports that 19% of all new US covid cases discovered between Aug. 2nd and Sept. 2nd can be traced back to the Sturgis motorcycle rally. Oddly enough, the headline reads 20% while the article text says 19%...go figure.
Quote:"We conclude that the Sturgis Motorcycle Rally generated public health costs of approximately $12.2 billion," the researchers wrote in a paper. "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend."https://www.foxnews.com/health/sturgis-motorcycle-rally-coronavirus-cases-south-dakota
At least one self-described pro-Trump news aggregator site (okay, it looks exactly like the fake news clickbait sites of 2015-2016) published an opinion that cited 196 cases as of Aug. 28th (article published Sept. 2nd). Naturally, this was shared with me by one of my acquaintances on Facebook with...extreme views.
But...Fox News! Note that they're reporting the same paper and figures that other less controversial news sites are reporting...and these figures are not charitable toward the idea that Sturgis covid fears were overblown.
This paper appears to have been published simultaneously by the Center for Health Economics and Policy Studies at San Diego State. (Direct link to PDF download) The SDSU version includes a note: "Dr. Sabia acknowledges support from the Center for Health Economics & Policy Studies at San Diego State University, including grant funding from the Troesh Family Foundation and the Charles Koch Foundation...." This may explain why Fox News was comfortable reporting the findings.
I guess I’m confused. The WaPo reports 260 cases, while saying that is low. This study says a couple hundred thousand - based on what. Certainly not contact tracing - pretty sure those at Sturgis aren’t going to be too inclined to submit. So how did they reach a number, which on first blush, looks to be preposterous. Also, I have to ask: do you consider the Center for Health Economics & Policy Studies at San Diego State University, to be unbiased?
(09-09-2020, 12:38 AM)lex24 Wrote:(09-09-2020, 12:09 AM)82 Card Wrote:(09-08-2020, 01:33 PM)fullmetal Wrote: Fox News reports that 19% of all new US covid cases discovered between Aug. 2nd and Sept. 2nd can be traced back to the Sturgis motorcycle rally. Oddly enough, the headline reads 20% while the article text says 19%...go figure.
Quote:"We conclude that the Sturgis Motorcycle Rally generated public health costs of approximately $12.2 billion," the researchers wrote in a paper. "This is enough to have paid each of the estimated 462,182 rally attendees $26,553.64 not to attend."https://www.foxnews.com/health/sturgis-motorcycle-rally-coronavirus-cases-south-dakota
At least one self-described pro-Trump news aggregator site (okay, it looks exactly like the fake news clickbait sites of 2015-2016) published an opinion that cited 196 cases as of Aug. 28th (article published Sept. 2nd). Naturally, this was shared with me by one of my acquaintances on Facebook with...extreme views.
But...Fox News! Note that they're reporting the same paper and figures that other less controversial news sites are reporting...and these figures are not charitable toward the idea that Sturgis covid fears were overblown.
This paper appears to have been published simultaneously by the Center for Health Economics and Policy Studies at San Diego State. (Direct link to PDF download) The SDSU version includes a note: "Dr. Sabia acknowledges support from the Center for Health Economics & Policy Studies at San Diego State University, including grant funding from the Troesh Family Foundation and the Charles Koch Foundation...." This may explain why Fox News was comfortable reporting the findings.
I guess I’m confused. The WaPo reports 260 cases, while saying that is low. This study says a couple hundred thousand - based on what. Certainly not contact tracing - pretty sure those at Sturgis aren’t going to be too inclined to submit. So how did they reach a number, which on first blush, looks to be preposterous. Also, I have to ask: do you consider the Center for Health Economics & Policy Studies at San Diego State University, to be unbiased? And while I smile at the glee that Fox reported it, what does that prove? Nothing. They reported what some group said.
I’ll betvright now 5his doesn’t hold up.
RE: Superspreading events (one study: 20% of cases) - magnus - 09-09-2020
Not that it completely explains the discrepancy but is 260 from outside the state and 19% includes locals? Though that would require a very high R value for local transmission no?
RE: lex24 - BostonCard - 09-09-2020
I don't know where they get that 20% of cases in the US can be traced to Strugis. The artice claims:
Quote:Finally, difference-in-differences (dose response) estimates show that following the Sturgis event, counties that contributed the highest inflows of rally attendees experienced a 7.0 to 12.5 percent increase in COVID-19 cases relative to counties that did not contribute inflows.
Basically, we are only talking about a 7 - 12.5% increase, and that is only in counties from which a lot of Sturgis participants came from. In South Dakota, where the rally occurred, the effect was larger ("This represents an increase of over 35 percent relative to the 9.7 cases per 1,000 population in South Dakota on July 31, 2020 (South Dakota Department of Health 2020).") you would expect the effect to dissipate pretty quickly outside the state.
(09-09-2020, 12:38 AM)lex24 Wrote: I guess I’m confused. The WaPo reports 260 cases, while saying that is low. This study says a couple hundred thousand - based on what. Certainly not contact tracing - pretty sure those at Sturgis aren’t going to be too inclined to submit. So how did they reach a number, which on first blush, looks to be preposterous. Also, I have to ask: do you consider the Center for Health Economics & Policy Studies at San Diego State University, to be unbiased?
The difference is between direct and indirect effects. The 260 represents the number of people who attended Sturgis and developed COVID-19 within the infectious period (~2 weeks) after the event. The study by Stavia includes direct and indirect effects; not just the people directly infected with COVID-19, but all the people they spread it to. From the paper (http://ftp.iza.org/dp13670.pdf):
Quote:Second, using data from the Centers for Disease Control and Prevention (CDC) and a synthetic control approach, we show that by September 2, a month following the onset of the Rally, COVID-19 cases increased by approximately 6 to 7 cases per 1,000 population in its home county of Meade. Finally, difference-in-differences (dose response) estimates show that following the Sturgis event, counties that contributed the highest inflows of rally attendees experienced a 7.0 to 12.5 percent increase in COVID-19 cases relative to counties that did not contribute inflows.
Note that the paper includes the corresponding author's contact information. My experience is that authors are generally very willing to discuss their work, e-mail him and ask. My own rather opinion based on a cursory examination is that there is nothing exotic or unusual about the methods the authors used (they approached it using the econometrics toolbox, not the public health toolbox; these are very similar, but you can tell from the fact that they did a "difference-in-difference" analysis that the authors were economists). The results are subject to the same biases that any observational study (one where there isn't a randomized, placebo controlled intervention) are subject to. As best I can tell, the authors made a good faithed effort to address the potential biases, but you can only address the biases you can think about, and there is always a possibility of residual confounding.
In my mind, the bottom line is that the study is solid and plausible but on its own should not be considered definitive.
BC
RE: Superspreading events (one study: 20% of cases) - BostonCard - 10-19-2020
(08-22-2020, 02:40 PM)fullmetal Wrote: It makes sense that those who slack on precautions would end up getting the disease...and that they would socialize with other like-minded people who don't take precautions seriously. (Not entirely sure that victims of a superspreading event are all necessarily cavalier about precautions, but I haven't seen data one way or the other.)
Tangent: The Sturgis motorcycle rally concluded recently. People are now looking for evidence of virus transmission and spread secondary to the event...there have been some, but the real question is if the infections are happening at a rate higher than that of background community spread. Being a motorcycle event, a lot of it was outside, but also being a party, there was a lot of indoor activity as well.
Yikes, Sturgis may have seeded the current wave happening in the midwest:
https://www.washingtonpost.com/health/2020/10/17/sturgis-rally-spread/?campaign_id=9&emc=edit_nn_20201019&instance_id=23266&nl=the-morning®i_id=112348342§ion_index=2§ion_name=the_latest_news&segment_id=41476&te=1&user_id=ceb8dc75e6018f57e5d7fc74f24220a2
Quote:Within weeks of the gathering, the Dakotas, along with Wyoming, Minnesota and Montana, were leading the nation in new coronavirus infections per capita. The surge was especially pronounced in North and South Dakota, where cases and hospitalization rates continued their juggernaut rise into October. Experts say they will never be able to determine how many of those cases originated at the 10-day rally, given the failure of state and local health officials to identify and monitor attendees returning home, or to trace chains of transmission after people got sick. Some, however, believe the nearly 500,000-person gathering played a role in the outbreak now consuming the Upper Midwest.
BC