What do people think of this preprint from March 13th? It suggests:
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R0=~5 in Wuhan in January (pre-containment measures)
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Infection fatality rate=~0.1% (several orders of magnitude smaller than the crude CFR estimated at 4.19%)
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~2 million infections in Wuhan on Jan 23rd / ~20% of people infected The authors are very reputable (GScholar profile first author, senior author, also quoted in the NYT). If this is true, might there be many more (asymptomatic) cases everywhere now than people think? [Reddit thread] From paper: "Recently more evidence suggests that a substantial fraction of the infected individuals with the novel coronavirus show little if any symptoms, which suggest the need to reassess the transmission potential of this emerging disease"
Like others I doubt the infection and fatailty rates because of South Korea and Diamond princess (if the author knew about how much this result conflicts with those datasets then its up to them to argue why the new paper is better). R0=5 isn’t completely unbelieveable. If the doubling time without containment measures is 2 days and the infective period is 12 days (i.e. 5 days incubation period and a week afterwards) then R0=5. Unfortunately based on the rather unbelievable infection and fatality rates I don’t think this paper really adds any evidence for this—it suggests the model is fatally flawed.
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True, but Diamond Princess is full of oldies, and, despite South Korea massive testing, there might be selection bias—I guess people would only get tested if they had some symptom or contact with other infected persons (perhaps you’re referring a more specific study?). Notice that, if the science study claiming 86% of the cases in Wuhan were undocumented were right, this would already imply a fatality rate of about 0.6%, below South Korea estimates. Yet, I agree the fatality rate is surprisingly low, and it’s just a statistical model.
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Diamond princess is important because they did 100% testing so it gives us an idea of asymptomatic : symptomatic ratio. The result was roughly 1:1, nothing like 50:1 or whatever this paper suggests. The science study with 6:1 is at least plausible if you account for symptomatics who weren’t identified. If South Korea hadn’t managed to test the majority of their cases then it is unlikely that they would have managed to reduce their infection rate so dramatically—their quarantine measures aren’t massively strict although I think the population are self-enforcing good practice pretty well. I doubt that Wuhan death rates could be below South Korean rates due to the acknowledged overcrowding in Wuhan. Again, 0.6% is kind of plausible, the model here (0.1%) isn’t.
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I’m sorry, I’m not sure if I understood the relevance of asymptomatic : symptomatic ratio here. I think what’s at stake in this article is the ratio undocumented : documented cases; it’ll include not only asymptomatic, pre-symptomatic or mildly symptomatic people, but people who got really sick but couldn’t be tested until Hubei had largely improved their testing capabilities. I do think a 50:1 rate is surprising, though not impossible. If 50% of the cases in South Korea are asymptomatic and so don’t get tested, their true death rate would be ~0.4-0.5%; if you add people who got sick before their testing capability was improved, etc., it may be lower. But again, I really prefer to be pessimistic in my death rates.
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If there is a 1:1 symptomatic:asymptomatic ratio and 2,000,000 odd infections then there are 1,000,000 symptomatic people out there and only 40,000 identified. Of that 1,000,000 we expect 200,000 to require hospitalisation and 50,000 to require ICU.
If this was true I would expect someone to have noticed.
There might be another explanation for the figures that I’m missing but, as I said, I think it’s up to them to explain what they think is going on.
More points in favor of a higher IFR:
The percentage of asymptomatic cases on the Diamond Princess was even lower than 50%. It was only about 18%. (I trust this figure because the paper has author overlap with the paper that gave a higher figure initially, and it’s written by the same author who made the 0.1% estimate and we’d expect this person to – if anything – have a bias toward expecting a larger number of asymptomatic cases).
About the age distribution on the Diamond Princess: I tried doing age adjustment for it here. ((Edited because I revised some estimates.))
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Maybe CDC screwed their data, but they say 46.5% of the Diamond Princess cases were asymptomatic when tested: https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e3.htm?s_cid=mm6912e3_w I believe this might be a confusion between asymptomatic and pre/mildly symptomatic—but whatever: the claim at stake is that there’s a ton of undocumented cases out there, not that they’re asymptomatic
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They write "at the time of testing." The study I cite followed up with what happened to patients. Also relevant: In the last 5 days, 3 more people who had tested positive on the Diamond Princess died. And one person died two weeks ago but somehow it wasn’t reported for a while. So while my own estimates were based on the assumption that 7 / 700 people died, it’s now 11 / 700.
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I noticed CDC claims 9 deaths from Diamond Princess, but I didn’t find support in their source. WHO is still counting 8 deaths. I guess you’re right, but I’d appreciate if you could provide the source.
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I read about the new deaths on the Wikipedia article. A Canadian man in his 70s died on 19 March, making him the ninth coronavirus-related death from the ship.> [102][46] Two Japanese passengers in their 70s died on 22 March.[47]--
South Korea
The Diamond Princess
China How much to count evidence from each data set depends on how much model uncertainty we have about the processes that generated the data, how fine-grained the reporting has been, and how large the sample sizes are. China is good on sample size but poor in every other respect. The cruise ship is poor on sample size but great in every other respect. South Korea is good in every respect. If I get lower bounds of 0.4% and 0.35% from the first two examples, and someone writes a new paper on China (where model uncertainty is by far highest) and gets a conclusion that is 16x lower than some other reputable previous estimates (where BTW no one has pointed out a methodological flaw either so far), it doesn’t matter whether I can find a flaw in the study design or not. The conclusion is too implausible compared to the paucity of the data set that it’s from. It surely counts as some evidence and I’m inclined to move a bit closer to my lower bounds, all else equal, but for me it’s not enough to overthrow other things that I believe we already know.
New editorial about the asymptomatic rate in Nature—the author of the preprint above are featured in this as well. They say asymptomatic and mild case rate might be up to 50% of all infections and that these people are infectious.
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And another preprint saying there were +700k cases in China on 13th of March: "Since severe cases, which more likely lead to fatal outcomes, are detected at a higher percentage than mild cases, the reported death rates are likely inflated in most countries. Such under-estimation can be attributed to under-sampling of infection cases and results in systematic death rate estimation biases. The method proposed here utilizes a benchmark country (South Korea) and its reported death rates in combination with population demographics to correct the reported COVID-19 case numbers. By applying a correction, we predict that the number of cases is highly under-reported in most countries. In the case of China, it is estimated that more than 700.000 cases of COVID-19 actually occurred instead of the confirmed 80,932 cases as of 3/13/2020." also implying a lower CFR than previously thought (perhaps less than 0.5%). 3k deaths in China / 700k actual cases)
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From the paper:
From the paper:
And yet another preprint estimating the R0 to be 26.5**:** Quotes from paper: "The size of the COVID-19 reproduction number documented in the literature is relatively small. Our estimates indicate that R0= 26.5, in the case that the asymptomatic sub-population is accounted for. In this scenario, the peek of symptomatic infections is reached in 36 days with approximately 9.5% of the entire population showing symptoms, as shown in Figure 3." I think they estimate about 1 million severe cases in the US alone if left unchecked at the peak. "It is unlikely that a pathogen that blankets the planet in three months can have a basic reproduction number in the vicinity of 3, as it has been reported in the literature (19–24). SARS-CoV-2 is probably among the most contagious pathogens known. Unlike the SARS-CoV epidemic in 2003 (25), where only symptomatic individuals were capable of transmitting the disease. Asymptomatic carriers of the COVID-19 virus are most likely capable of transmission to the same degree as symptomatic." "This study shows that the population of individuals with asymptomatic COVID-19 infections are driving the growth of the pandemic. The value of R0 we calculated is nearly one order of magnitude larger than the estimates that have been communicated in the literature up to this point in the development of the pandemic"
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from supplementary materials: "DISCLAIMER: The following estimates were computed using 2010 US Census data with 2016 population projections and the percentages of clinical cases and mortality events reported in Mainland China by the Chinese Center for Disease Control as of February 11th, 2020. CCDC Weekly / Vol. 2 / No. 8, page 115, Table 1. The following estimates represent a worst-case scenario, which is unlikely to materialize. • Maximum number of symptomatic cases = 34,653,921 • Maximum number of mild cases = 28,035,022 • Maximum number of severe cases = 4,782,241 • Maximum number of critical cases = 1,628,734 • Maximum number of deaths = 3,439,516" https://drive.google.com/drive/folders/18qaRKnQG1GoXamnzJwkHu2GG9xCe4w8_
Another preprint suggesting that half or more of the UK population is already infected: FT coverage: https://www.ft.com/content/5ff6469a-6dd8-11ea-89df-41bea055720b study: https://www.dropbox.com/s/oxmu2rwsnhi9j9c/Draft-COVID-19-Model%20%2813%29.pdf?dl=0