Epistemic status: very, very uncertain. Please continue following official advice like social distancing etc.
I've seen all the previous discussions (including in this thread and on Tyler Cowen's blog, but remain unconvinced]
A preprint from 24/03 by Gupta et al. at Oxford suggests that the current data on C19 is consistent with both:
- Few infections, low infectiousness (r0), and high infection fatality rate (IFR)
- Widespread actual (asymptomatic) infections, high r0 and low IFR
For instance, the authors suggest that if the IFR is low and C19 is very infectious, it is possible that by 19/03, 36%-68% of the UK population would have already been infected with C19. The ongoing epidemics in the UK and Italy started at least a month before the first reported death.
Here I make the strongest possible case that C19 is widespread, r0 is underestimated and IFR is low.
I base this on the following:
- Much C19 transmission might be asymptomatic and presymptomatic.,
- Tim Spector, professor of genetic epidemiology a King's College London, finds that
- 10% of 650,000 UK users of their C19 symptom tracker app showed mild symptoms. Thus 6.5m people in UK are infected, not taking into account asymptomatic cases
- A preprint from 26/03 by epidemiologists Gutierrez et al., Professor and Chair of Mathematics at University of Texas at San Antonio (Google Scholar Profile) suggests
- An R0 between 5.5 and 25.4, if you account for asymptomatic spread. In this scenario, the peak of symptomatic infections is reached in 36 days with approximately 9.5% of the entire population showing symptoms.
- The authors argue that it’s unlikely for a pathogen to blanket the planet in three months with an R0= ~3 and that it has to be more contagious than measles, which has an R0 of 18.
- A preprint from 13/03 by Chowell et al., Professor & Chair - Georgia State University School of Public Health suggesting (GScholar profile first author who has written 2 papers on the Diamond Princess, senior author quoted in the NYT) suggests that
- r0=5.20 (95%CrI: 5.04-5.47)
- IFR=0.12% (95%CrI: 0.08-0.17%), several orders of magnitude smaller than the crude CFR estimated at 4.19%.
- ~20% of the all people in Wuhan were infected on Jan 23rd (~2 million infections)
- A preprint from 24/03 by French epidemiologists (Google Scholar profile) suggesting:
- “The actual infections France is probably much higher than the observations: we find here a factor ×15 (95%-CI: 4 − 33), which leads to a 5.2/1000 mortality rate (95%-CI: 1.5/1000 − 11.7/1000) at the end of the observation period. We find a R0 of 4.8, a high value which may be linked to the long viral shedding period of 20 days r0=4.8”
- Oxford University Evidence Service meta-analysis suggests that as of 22/03 that the IFR=~0.29% (95% CI, 0.25 to 0.33). Widespread testing (which isn’t random) in Iceland suggests an even lower IFR.
- A British Medical Journal editorial from 20/03 arguing that C19 fatality is likely overestimated 
- The Imperial study is based on “thousands of lines of undocumented C [code] from 13+ years ago to model flu pandemics”
- Dengue tests react to C19 and many could be false positives according to a Lancet paper
- Dengue fever crisis grips Latin America | News
- Through the week ending March 13, Paraguay has reported 203,922 total dengue fever cases, including 51 deaths. This compares to 669 dengue cases reported during the same period in 2019."
- Singapore which is said to have very good containment of C19, reports a recent dengue outbreak (4000 cases) doubled from previous year
- There were a few dengue in Australia and Florida where it is unusual
- High proportion of special populations are infected (celebrities, athletes and politicians). For instance, very many Iranian politicians have C19. This suggests that if the whole population had access to frequent tests like those special groups would have, then we would see many more cases. Fatalities are also very high amongst people with very high age and many comorbidities, suggesting that there are many asymptomatic infections amongst the young.
- C19 has been detected in wastewater in the Netherlands. If the test is not very sensitive, this would suggest C19 is widespread.
- “From 17 February 2020 on, weekly wastewater samples were taken at Schiphol Airport. During the first two weeks, the virus that causes COVID-19 was not detected. However, the genetic material from the virus was detected in the airport wastewater samples taken on 2, 9 and 16 March. The first sample containing the virus was taken four days after the first person in the Netherlands tested positive for COVID-19 on 27 February. Genetic material from the virus was detected in wastewater samples taken from the wastewater treatment plant in Tilburg on 3, 10 and 17 March.”
- Concentration and detection of SARS coronavirus in sewage from Xiao Tang Shan Hospital and the 309th Hospital of the Chinese People's Liberation Army.
- Wastewater-based epidemiology biomarkers: Past, present and future
- PCR test have a high false negative rate
- They can only detect the virus for ~1 week
- Difficulties in False Negative Diagnosis of Coronavirus Disease 2019: A Case Report. Note that this was a highly symptomatic person.
- One person had persistent negative swab, but tested positive through fecal samples.
- “If the samples are not correctly stored and handled, the test may not work. There has also been some discussion about whether doctors testing the back of the throat are looking in the wrong place. This is a deep lung infection rather one in the nose and throat.”
- 71% accurate the first time people are tested. The other 29%, the test showed negative even though they really had it.
- Infections in China might be underestimated because:
- Hidden infections challenge China’s claim coronavirus is under control
- “Chinese journalists have uncovered other cases of people testing negative six times before a seventh test confirmed they had the disease.”
- “There have been reports that early Chinese tests may have had a false negative rate as high as 50%.”
- Analysts have doubted the near-zero transmission rate in China for various reasons such as people with no symptoms being denied testing.
- Early Chinese tests may have had a false negative rate as high as 50%.
- Czech Researchers claim that Chinese do not work well
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