Thanks for doing the math, I think this is valuable even with a basic model.
I think this analysis undercounts the impact of spreading the virus. You only model local community transmission, but if the epidemic doesn’t burn out in the Seattle area, it’ll cause additional community spread elsewhere, which leaves room for another lg(8B/4M) = 11 doublings.
A linear reduction in R also might be too optimistic. In the plausible worst case, R is nearly constant until the final few generations when it saturates and starts to burn out.
I agree that it is useful to make simple models. The consensus appears to be that there will be a global spread, so then it appears that short-term actions could have very high impact. However, one could also argue that then the end state is going to be the same, so that would mean short-term actions would have no impact. It is true if social distancing (physical distance, handwashing, gloves, masks, etc.) is maintained for the entire pandemic, then R0 falls below one sooner, so fewer people get the disease. You can see a model of this here. On the 80,000 Hours podcast, they say that reducing travel out of the place of origin by 90% in the beginning only delays the outbreak 3 weeks, likely not enough time to get a vaccine. So which one is right, a huge impact due to short-term actions or basically nothing?
Presumably the benefit comes from flattening the curve. I.e. if we don’t introduce control measures, the demands on the healthcare system will be unmanageable, whereas if we spread them out, then the healthcare system can cope with the demand.
The syntax for embedding images is . For this and other forum formatting issues, try googling along the lines of “markdown insert image” or “markdown cheatsheet” (still what I do despite using markdown regularly)
I agree that if we have sustained protective measures, it would not only lower the peak but also reduce the total number of people exposed. However, I am defining a short-term action as doing something we would not normally do in the next few weeks, like canceling a conference or early travel bans. I think this would delay the peak, but it’s not clear to me that the peak would be appreciably lower. Furthermore, this says there are about 60,000 full function ventilators and 160,000 total ventilators. If 10% percent of people are infected at the peak and 3% of those require ventilation, that would be 1 million requiring ventilation. So even in the US, and with moderate protective measures, it looks like most people would not be getting the ventilation they need (though lowering the peak will still help somewhat). Of course if the protective measures actually stopped the spread early, then that would be a big benefit.
I don’t expect the outbreak to continue indefinitely in the US, Europe, or East Asia. As noted at https://www.linkedin.com/pulse/bending-curve-covid-19-how-avoid-being-wuhan-lombardy-scott-leibrand/ , we are likely to need to implement 50-75% social distancing in order to avoid overloading ICU capacity, and at that point we’ve also basically stopped growth in new cases, making it comparatively easy to keep doing more of the same until new cases start to noticeably shrink, as they did in China, Singapore, and now Korea. The real question to me is how long it takes us to bring R down to and below 1. As lunis did, I originally thought that 1 month was optimistic, but Washington State has surprised me, and seems to have implemented the necessary social distancing after about 2 weeks (mostly in the last 2 days). As a result, my estimates of the value of individual actions may have been slightly overestimated. But this is one area where I’m happy to have been wrong, as it means people were listening and finally did the right thing. :-)
Thanks for doing the math, I think this is valuable even with a basic model.
I think this analysis undercounts the impact of spreading the virus. You only model local community transmission, but if the epidemic doesn’t burn out in the Seattle area, it’ll cause additional community spread elsewhere, which leaves room for another lg(8B/4M) = 11 doublings.
A linear reduction in R also might be too optimistic. In the plausible worst case, R is nearly constant until the final few generations when it saturates and starts to burn out.
I agree that it is useful to make simple models. The consensus appears to be that there will be a global spread, so then it appears that short-term actions could have very high impact. However, one could also argue that then the end state is going to be the same, so that would mean short-term actions would have no impact. It is true if social distancing (physical distance, handwashing, gloves, masks, etc.) is maintained for the entire pandemic, then R0 falls below one sooner, so fewer people get the disease. You can see a model of this here. On the 80,000 Hours podcast, they say that reducing travel out of the place of origin by 90% in the beginning only delays the outbreak 3 weeks, likely not enough time to get a vaccine. So which one is right, a huge impact due to short-term actions or basically nothing?
Presumably the benefit comes from flattening the curve. I.e. if we don’t introduce control measures, the demands on the healthcare system will be unmanageable, whereas if we spread them out, then the healthcare system can cope with the demand.
I don’t know how to add images in comments, so here’s a link to a relevant image: https://imgur.com/ckt0ujv
And this is the article the image came from: https://www.vox.com/science-and-health/2020/3/6/21161234/coronavirus-covid-19-science-outbreak-ends-endemic-vaccine
This version that has been making the rounds on twitter makes the point even plainer:
The syntax for embedding images is
. For this and other forum formatting issues, try googling along the lines of “markdown insert image” or “markdown cheatsheet” (still what I do despite using markdown regularly)I agree that if we have sustained protective measures, it would not only lower the peak but also reduce the total number of people exposed. However, I am defining a short-term action as doing something we would not normally do in the next few weeks, like canceling a conference or early travel bans. I think this would delay the peak, but it’s not clear to me that the peak would be appreciably lower. Furthermore, this says there are about 60,000 full function ventilators and 160,000 total ventilators. If 10% percent of people are infected at the peak and 3% of those require ventilation, that would be 1 million requiring ventilation. So even in the US, and with moderate protective measures, it looks like most people would not be getting the ventilation they need (though lowering the peak will still help somewhat). Of course if the protective measures actually stopped the spread early, then that would be a big benefit.
I don’t expect the outbreak to continue indefinitely in the US, Europe, or East Asia. As noted at https://www.linkedin.com/pulse/bending-curve-covid-19-how-avoid-being-wuhan-lombardy-scott-leibrand/ , we are likely to need to implement 50-75% social distancing in order to avoid overloading ICU capacity, and at that point we’ve also basically stopped growth in new cases, making it comparatively easy to keep doing more of the same until new cases start to noticeably shrink, as they did in China, Singapore, and now Korea. The real question to me is how long it takes us to bring R down to and below 1. As lunis did, I originally thought that 1 month was optimistic, but Washington State has surprised me, and seems to have implemented the necessary social distancing after about 2 weeks (mostly in the last 2 days). As a result, my estimates of the value of individual actions may have been slightly overestimated. But this is one area where I’m happy to have been wrong, as it means people were listening and finally did the right thing. :-)