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What if the k for Covid-19 is .1? - Printable Version

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What if the k for Covid-19 is .1? - Snorlax94 - 05-22-2020

https://www.sciencemag.org/news/2020/05/why-do-some-covid-19-patients-infect-many-others-whereas-most-don-t-spread-virus-all

That’s why in addition to R, scientists use a value called the dispersion factor (k), which describes how much a disease clusters. The lower k is, the more transmission comes from a small number of people. In a seminal 2005 Nature paper, Lloyd-Smith and co-authors estimated that SARS—in which superspreading played a major role—had a k of 0.16. The estimated k for MERS, which emerged in 2012, is about 0.25. In the flu pandemic of 1918, in contrast, the value was about one, indicating that clusters played less of a role.

Estimates of k for SARS-CoV-2 vary. In January, Julien Riou and Christian Althaus at the University of Bern simulated the epidemic in China for different combinations of R and k and compared the outcomes with what had actually taken place. They concluded that k for COVID-19 is somewhat higher than for SARS and MERS. That seems about right, says Gabriel Leung, a modeler at the University of Hong Kong. “I don’t think this is quite like SARS or MERS, where we observed very large superspreading clusters,” Leung says. “But we are certainly seeing a lot of concentrated clusters where a small proportion of people are responsible for a large proportion of infections.” But in a recent preprint, Adam Kucharski of LSHTM estimated that k for COVID-19 is as low as 0.1. “Probably about 10% of cases lead to 80% of the spread,” Kucharski says.”

https://wellcomeopenresearch.org/articles/5-67

If the k(dispersion factor) is .1, and if 10% of the cases lead to 80% of the spread, I would think this would place even more emphasis on closing even medium-sized venues and on employee and customer screening. It’d also make 100% enforcement of mask wearing all the more important.


RE: What if the k for Covid-19 is .1? - 2006alum - 05-22-2020

I posted this same study here but no one else responded. If they're right, one important thing is that we need to worry more about superspreading events/individuals, rather than more low-key person to person transmission. Given that early conference in Boston, Mardi Gras in New Orleans, and several churches, choirs, and funerals, there's a possible emerging picture that most transmission occurs when a virally shedding individual is in a confined or crowded space for an extended period of time such that they can expose numerous others to it.

Now of course, it's much easier to identify these super-spreading events than the lower-key transmission from one household member to another, but given that many places that are reopening are not yet seeing a significant increase in new cases even several weeks in, that suggests to me that the highest risk economic activities may be the ones that have yet to re-open: concerts, movie theaters, conferences, parties, crowded indoor restaurants, schools, etc. 

That suggests that we might be able to keep the transmission at an ~R0 while being able to do 80% of our normal activities with masks, socially distanced, and with other minor inconveniences to quality of life. Apart from schools, air transit, and public transportation, most of the other activities mentioned above, while certainly economically important, are not socially necessary in the next year. But those are three of immense proportions caveats, and I've been on record for quite a while now as being in disbelief that NYC will be able to resume as normal prior to a vaccine, given the unavoidable social crowding that is the MTA system. Schools, of course, will be another of immense proportions issue.


RE: What if the k for Covid-19 is .1? - Snorlax94 - 05-22-2020

(05-22-2020, 03:42 PM)2006alum Wrote:  I posted this same study here but no one else responded. If they're right, one important thing is that we need to worry more about superspreading events/individuals, rather than more low-key person to person transmission. Given that early conference in Boston, Mardi Gras in New Orleans, and several churches, choirs, and funerals, there's a possible emerging picture that most transmission occurs when a virally shedding individual is in a confined or crowded space for an extended period of time such that they can expose numerous others to it.

Now of course, it's much easier to identify these super-spreading events than the lower-key transmission from one household member to another, but given that many places that are reopening are not yet seeing a significant increase in new cases even several weeks in, that suggests to me that the highest risk economic activities may be the ones that have yet to re-open: concerts, movie theaters, conferences, parties, crowded indoor restaurants, schools, etc. 

That suggests that we might be able to keep the transmission at an ~R0 while being able to do 80% of our normal activities with masks, socially distanced, and with other minor inconveniences to quality of life. Apart from schools, air transit, and public transportation, most of the other activities mentioned above, while certainly economically important, are not socially necessary in the next year. But those are three of immense proportions caveats, and I've been on record for quite a while now as being in disbelief that NYC will be able to resume as normal prior to a vaccine, given the unavoidable social crowding that is the MTA system. Schools, of course, will be another of immense proportions issue.
You're right 2006alum -- I even highlighted the same excerpt you had originally pointed out -- my bad!

Should I delete the post? Fold it into the prior thread?

My only very weak defense is that  the previous thread drifted a little so I didn't immediately associate it.


RE: What if the k for Covid-19 is .1? - 2006alum - 05-22-2020

(05-22-2020, 03:55 PM)Snorlax94 Wrote:  You're right 2006alum -- I even highlighted the same excerpt you had originally pointed out -- my bad!

Should I delete the post? Fold it into the prior thread?

My only very weak defense is that  the previous thread drifted a little so I didn't immediately associate it.

Nah we're all good. Mostly I was just disappointed no one else responded because I thought a k of .1 to be a potential gamechanger if true. I probably should have labelled the thread more clearly. Thanks for restarting this discussion.

But clearly you and I are on the same wavelength across three different threads right now! ;) (re: appeal of WFH and also First Amendment applications to the lockdowns).


RE: What if the k for Covid-19 is .1? - BostonCard - 05-22-2020

I don’t know that I would call it a game changer, but it would make it much easier to control if you can figure out what leads to a superspreading event and stop it.  If, on the hand, there is no patter pun to the superspreading events, then your approach to limiting spread would be the same.

BC


RE: What if the k for Covid-19 is .1? - Snorlax94 - 05-22-2020

(05-22-2020, 07:09 PM)BostonCard Wrote:  I don’t know that I would call it a game changer, but it would make it much easier to control if you can figure out what leads to a superspreading event and stop it.  If, on the hand, there is no patter pun to the superspreading events, then your approach to limiting spread would be the same.

BC
What is a patter pun? (I am guessing you are using a smartphone that’s auto-“correcting” pattern?)

To me, if superspreaders alone counted for 80% of cases, that alone is an actionable pattern. It puts more weight on limiting even medium-sized gatherings and because several super spreaders were symptomatic (including the choir singer in Seattle, the church member in Daegu, the tech worker in Seattle...), it puts more emphasis on screening people anywhere people gather (mall and workplace entrances). It’s sad to think if the R0 was 3, then it could be .6 if we could just stop the symptomatic superspreaders from going to work, the festival or church.


RE: What if the k for Covid-19 is .1? - BostonCard - 05-23-2020

Yes, it was an autocorrect.  And it mangled it so much that I don't know what that was supposed to have been.

But basically, what I was trying to say is that if it is impossible to predict the characteristics that would lead to a superspreading event, then you are correct that the only way to do anything is to limit even medium sized gatherings.

BC


RE: What if the k for Covid-19 is .1? - magnus - 05-23-2020

patter pun = "pattern" + "rhyme or reason"?


RE: What if the k for Covid-19 is .1? - BostonCard - 05-23-2020

(05-23-2020, 11:43 AM)magnus Wrote:  patter pun = "pattern" + "rhyme or reason"?

Good inference.  I think you are correct.

BC


RE: What if the k for Covid-19 is .1? - 2006alum - 05-24-2020

More on the role of superspreaders: