[2006alum]

This is probably the best recent read I've seen on this:

[tweet]https://twitter.com/kakape/status/1262863846387134470?s=20[/tweet]

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.

That could explain some puzzling aspects of this pandemic, including why the virus did not take off around the world sooner after it emerged in China, and why some very early cases elsewhere—such as one in France in late December 2019, reported on 3 May—apparently failed to ignite a wider outbreak. If k is really 0.1, then most chains of infection die out by themselves and SARS-CoV-2 needs to be introduced undetected into a new country at least four times to have an even chance of establishing itself, Kucharski says. If the Chinese epidemic was a big fire that sent sparks flying around the world, most of the sparks simply fizzled out.

There's still a lot we don't know about COVID-19, obviously, but my guess is that the reason why we aren't seeing a brobdingnagian increase in COVID-19 cases as lockdowns are lifted is that the likely superspreader activities - crowded classrooms, open floor plan offices, choir practices, church services, movie theaters, sit-down restaurants, and dense mass transit - haven't resumed anywhere near to normal yet.

This is an entirely educated guess, but I am coming to the view that if we wear masks, avoid staying in crowded or confined spaces for more than a moment or two, and try to socialize outdoors as much as possible (easier to do in the summer, obviously), then we can keep the virus transmission low while being able to do ~70% of our normal activities. I'll be avoiding all of the above for the foreseeable future, but I increasingly think that picnics, outdoor exercise, counter take-away food service, and short-term visits to stores are all fairly low risk provided people keep a safe distance and don't linger near one another.

Of course, that's not going to save the restaurant industry, the commercial real estate industry, theme parks, movie theaters, or public transit systems. But it does give me hope that we can find a balance between "reopen everything" and "lockdown for 18 months."

[2006alum]

This is probably the best recent read I've seen on this:

[tweet]https://twitter.com/kakape/status/1262863846387134470?s=20[/tweet]

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.

That could explain some puzzling aspects of this pandemic, including why the virus did not take off around the world sooner after it emerged in China, and why some very early cases elsewhere—such as one in France in late December 2019, reported on 3 May—apparently failed to ignite a wider outbreak. If k is really 0.1, then most chains of infection die out by themselves and SARS-CoV-2 needs to be introduced undetected into a new country at least four times to have an even chance of establishing itself, Kucharski says. If the Chinese epidemic was a big fire that sent sparks flying around the world, most of the sparks simply fizzled out.

There's still a lot we don't know about COVID-19, obviously, but my guess is that the reason why we aren't seeing a brobdingnagian increase in COVID-19 cases as lockdowns are lifted is that the likely superspreader activities - crowded classrooms, open floor plan offices, choir practices, church services, movie theaters, sit-down restaurants, and dense mass transit - haven't resumed anywhere near to normal yet.

This is an entirely educated guess, but I am coming to the view that if we wear masks, avoid staying in crowded or confined spaces for more than a moment or two, and try to socialize outdoors as much as possible (easier to do in the summer, obviously), then we can keep the virus transmission low while being able to do ~70% of our normal activities. I'll be avoiding all of the above for the foreseeable future, but I increasingly think that picnics, outdoor exercise, counter take-away food service, and short-term visits to stores are all fairly low risk provided people keep a safe distance and don't linger near one another.

Of course, that's not going to save the restaurant industry, the commercial real estate industry, theme parks, movie theaters, or public transit systems. But it does give me hope that we can find a balance between "reopen everything" and "lockdown for 18 months."