Elon Musk on Twitter
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So, let's look at that claim. From the Lancet:
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30746-7/fulltext
"Given the intensive, proactive case finding and the sharp drop in reported cases outside Hubei during February, 2020, the ascertainment rates in these cities were probably very high."
"As of Feb 29, 2020, there were 411 (Beijing),
337 (Shanghai), 417 (Shenzhen), and 504 (Wenzhou) laboratory-confirmed cases of COVID-19 infections reported."
In spite of this, I'll assume they are missing 90% of the cases, though (not possible if they are not having an out of control outbreak BTW). Just for good measure. (For the record, they have had 7 reported deaths to date in Shanghai, which would produce an estimation of about 700 cases to date.) My assumption is suggesting they have had more like 6000 cases (they have had 657 confirmed cases reported to date), so I am very likely overestimating by at least a factor of 5!
Greater China: coronavirus statistics by region | Statista
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The Shanghai Gigafactory reopened on February 10th.
Coronavirus: Tesla Giga Shanghai reopening on Feb 10, Shanghai govt offers help - Electrek
I count 42 cases in Shanghai (not including from international travel)
after February 10th. So using 10x,
assume 420 cases after reopening. Max. Daily rate appears to be at most about 1-2 per day on average (convert to 20 per day using 10x factor)
Shanghai population: 24.3 million
Cases per capita, Shanghai,
total, after reopening: 420/24.3e6 =
17.3 ppm
Cases per capita per day after reopening, Shanghai: 2 cases per/day /24.3 million: 0.08 ppm per day
Again, likely overestimating the disease burden by a lot here (I would guess about 5x, so more reasonable might be 0.016ppm per day)!
Alameda County, I will assume is
undercounting by a factor of 5x, rather than 10x (seems maybe reasonable given the number of deaths - they have had 71 deaths, which would suggest about 10k cases, since only maybe 7k would have resulted in death yet):
http://www.acphd.org/2019-ncov.aspx
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So that would give 5*2023 cases = 10115 cases. Population: 1.67 million
Cases per capita, Alameda County, prior to reopening: 10115/1.67e6 = 0.61%, or 6056 ppm
(This is probably a pretty good estimate, no overcount/undercount.)
If you want to use just the zip code of the Gigafactory (unreasonable), you get:
Cases per capita, 94538: 40*10/65954 = 0.6% (Same answer - it is pretty much the average of the county.)
Going forward, let's assume we are currently at the 50 new cases per day -> Let's assume they are doing a better job of testing now than in the past, though, and are only missing
half the cases (2x undercount). So translate to
100 cases per day for the 2x undercount:
Cases per capita, Alameda County, per day, as of today: 100/1.67e6 = 60ppm per day
Again, this is probably a very reasonable estimation of the rate, given the number of deaths.
Summary of veracity of Elon's claim:
Shanghai disease burden: 0.08ppm per day, average, after February 10th (now pretty much zero...)
Alameda County disease burden: 60 ppm per day as of May 9th
Difference: 750x the disease burden in Alameda county, and if you assume a 5x overcount in Shanghai, it is closer to 3750x.
Conclusion: I am not sure that the Shanghai experience will translate well to the Alameda County situation - it seems like they should wait until disease burden is at least a factor of 5 lower, and even then, implement additional controls (testing!).
To put it another way, on any given day, assuming 10k workers in both Shanghai and Fremont:
In Shanghai, there are about 0.0008 workers per day entering the factory with a new case of coronavirus. (Probably much lower number now though, since there appear to be zero cases except at the airport.)
In Fremont, there would be about 0.6 workers per day entering the factory with a shiny new case of the 'rona.
If they were to open up next week, I would expect them to be able to go no more than about 2 weeks without having an outbreak (accounting for some risk reduction due to screening, etc.). Could relatively easily be less than a week.
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EDIT: While doing my per day numbers, I somehow managed to get Alameda County off by a factor of 100! It's way worse than what I said originally...
Would love someone to check the numbers to make sure I didn't make a mistake. Really will be useful for predicting future stock price trends (if/when factory reopens), is my guess. So I definitely want to have the right order of magnitude.