Starting at the end, the polling site 538 has done an excellent job in applying some probability – which is their area of expertise – to these wide ranges of predictions by epidemiological experts.

So let’s look at what four experts in infectious disease have to say specifically about the models upon which we’re making such huge political and economic decisions.

  1. Dr. Deborah Birx, Clinical Immunology, US Army
  2. Dr. Paul Auwaerter, Clinical Director, Infectious Diseases, Johns Hopkins
  3. Dr Eran Bendavid and Dr Jay Bhattacharya, Standford professors of medicine
  4. John P.A. Ioannidis — Stanford professor of epidemiology and population health

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1, Because it’s worth showing Dr Birx again as she talks about the Imperial College model.

 
  • So in the model, to get the numbers of infected people predicted, from which other projections of hospitalisations and death tolls are derived, you have to have either:
    • A large group of asymptomatic people who have never presented for any test. That’s possible but to determine that in fact, much testing is going on, Yet – “In no country have we seen an attack rate of more than one in a thousand.“
    • Or a transmission rate that’s very different from what is being seen on the ground.
  • But the predictions of such models don’t match the reality of what they’re seeing on the ground in Italy, South Korea and China.
  • If you did the divisions according to the models, Italy should have 400,000 deaths. They’re not even close to that.
  • “Models are models. There’s enough data now of the real experience with the coronavirus on the ground to make these predictions much more sound.”
  • “When people start talking about 20 percent of a population getting infected, it is very scary but we don’t have data that matches that based on the experience.“
  • “There’s no reality on the ground where we can see that 60 to 70 percent of Americans are going to get infected in the next eight to 12 weeks“.

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2.  Dr. Paul Auwaerter talks about the infection / transmission rate

If you have a COVID-19 patient in your household, your risk of developing the infection is about 10%….If you were casually exposed to the virus in the workplace (e.g., you were not locked up in conference room for six hours with someone who was infected [like a hospital]), your chance of infection is about 0.5%

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3. Dr Eran Bendavid and Dr Jay Bhattacharya

a) Testing vs infected population

“…First, the test used to identify cases doesn’t catch people who were infected and recovered. Second, testing rates were woefully low for a long time and typically reserved for the severely ill. Together, these facts imply that the confirmed cases are likely orders of magnitude less than the true number of infections. Epidemiological modelers haven’t adequately adapted their estimates to account for these factors.

b)  The number of US people infected and the US mortality rate

The epidemic started in China sometime in November or December. The first confirmed U.S. cases included a person who traveled from Wuhan on Jan. 15, and it is likely that the virus entered before that: Tens of thousands of people traveled from Wuhan to the U.S. in December. Existing evidence suggests that the virus is highly transmissible and that the number of infections doubles roughly every three days.

An epidemic seed on Jan. 1 implies that by March 9 about six million people in the U.S. would have been infected. As of March 23, according to the Centers for Disease Control and Prevention, there were 499 Covid-19 deaths in the U.S. If our surmise of six million cases is accurate, that’s a mortality rate of 0.01%, assuming a two week lag between infection and death. This is one-tenth of the flu mortality rate of 0.1%…”

This point is crucial and is much debated. One of the Trump taskforce has argued in the NEJM that the final mortality rate is likely to be between 0.1 and 1.0% – but has also said that the virus could be ten times more deadly than the flu, if it approaches the upper bound of his estimate. Both his arguments could be correct. It should also be noted here that Dr Birx above does not see – from the actual evidence to date – that there could be 6 million infected people in the US as of March 9)

c) The Italian and Chinese actual mortality rates.

“…Fear of Covid-19 is based on its high estimated case fatality rate – 2% to 4% of people with confirmed Covid-19 have died, according to the World Health Organization and others. So if 100 million Americans ultimately get the disease, two million to four million could die. We believe that estimate is deeply flawed. The true fatality rate is the portion of those infected who die, not the deaths from identified positive cases…

“…On or around Jan. 31, several countries sent planes to evacuate citizens from Wuhan, China. When those planes landed, the passengers were tested for Covid-19 and quarantined. After 14 days, the percentage who tested positive was 0.9%. If this was the prevalence in the greater Wuhan area on Jan. 31, then, with a population of about 20 million, greater Wuhan had 178,000 infections, about 30-fold more than the number of reported cases. The fatality rate, then, would be at least 10-fold lower than estimates based on reported cases.

Next, the northeastern Italian town of Vò, near the provincial capital of Padua. On March 6, all 3,300 people of Vò were tested, and 90 were positive, a prevalence of 2.7%. Applying that prevalence to the whole province (population 955,000), which had 198 reported cases, suggests there were actually 26,000 infections at that time. That’s more than 130-fold the number of actual reported cases. Since Italy’s case fatality rate of 8% is estimated using the confirmed cases, the real fatality rate could in fact be closer to 0.06%…”

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4. John P.A. Ioannidis

This was written on March 17 and while testing in many countries has ramped up massively since then his point still stands:

The data collected so far on how many people are infected and how the epidemic is evolving are utterly unreliable. Given the limited testing to date, some deaths and probably the vast majority of infections due to SARS-CoV-2 are being missed. We don’t know if we are failing to capture infections by a factor of three or 300.

This evidence fiasco creates tremendous uncertainty about the risk of dying from Covid-19. Reported case fatality rates, like the official 3.4% rate from the World Health Organization, cause horror — and are meaningless. Patients who have been tested for SARS-CoV-2 are disproportionately those with severe symptoms and bad outcomes. As most health systems have limited testing capacity, selection bias may even worsen in the near future.

It’s quite obvious that whatever decision governments make are going to be rolling the dice. South Korea, Taiwan and Singapore threw resources at testing and tracking which is risky but seems to have worked. Holland has gone for the herd immunity approach: given their enthusiasm for euthanasia that should not come as a surprise. Sweden also seems to be taking a relaxed approach. Given its Federal nature the USA has different approaches being taken by different states. New Zealand and other nations have gone for a fairly hardline lockdown that may burn to the ground a substantial part of the economy.

“Draconian countermeasures have been adopted in many countries. If the pandemic dissipates — either on its own or because of these measures — short-term extreme social distancing and lockdowns may be bearable,”
…
“How long, though, should measures like these be continued if the pandemic churns across the globe unabated? How can policymakers tell if they are doing more good than harm?”

Well the answer is that they can’t. They may never even be able to point to the number of lives saved, and even if they do there will be lives lost because of the lockdown. The phrase “Excess Deaths”, calculated at the end of 2020, may be the best measurement.
 
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