We Just Don’t Know

At the Wall Street Journal Eran Bendavid and Jay Bhattacharya explain why COVID-19 may be a lot less deadly than the present reaction would seem to indicate:

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.

The latter rate is misleading because of selection bias in testing. The degree of bias is uncertain because available data are limited. But it could make the difference between an epidemic that kills 20,000 and one that kills two million. If the number of actual infections is much larger than the number of cases—orders of magnitude larger—then the true fatality rate is much lower as well. That’s not only plausible but likely based on what we know so far.

Population samples from China, Italy, Iceland and the U.S. provide relevant evidence. On or around Jan. 31, 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%.

In Iceland, deCode Genetics is working with the government to perform widespread testing. In a sample of nearly 2,000 entirely asymptomatic people, researchers estimated disease prevalence of just over 1%. Iceland’s first case was reported on Feb. 28, weeks behind the U.S. It’s plausible that the proportion of the U.S. population that has been infected is double, triple or even 10 times as high as the estimates from Iceland. That also implies a dramatically lower fatality rate.

What all of this tells us is that we just don’t know. Ignore the Chinese statistics. We should treat them a PR rather than a guide for policy. But the findings from Italy and Iceland, in particular, are interesting. A mortality rate of 2% with a prevalence of 1% is more analogous to another seasonal flu than it is to the Black Death.

I want to emphasize three things. First, the purpose of the lockdowns, bans on large gatherings, and so on is not to reduce the number of people who will become infected by COVID-19. It is to pace the number of those who become seriously ill so that they do not overwhelm our health care system. It would be tragically irresponsible if we do not, simultaneous with that attempt, exert at least as much effort to increasing the size of the available resource with all due speed.

We have no reason to believe that COVID-19 won’t be with us forever. It should be obvious that the lockdowns can’t persist forever. What is needed is a modus vivendi with the persistent presence of COVID-19. As I have been pointing out we have lived with diseases that can kill before and we will need to learn to do so again.

Finally, we simply do not know and just “more testing” will not provide us with the knowledge we need. We need well-designed epidemiological testing before we really can understand the scope of what we’re dealing with. Diagnostic testing of individuals who present themselves at the hospital or putative testing centers won’t do that. Such testing would be a good job for the federal government but, if Washington won’t do it, we may be forced to do it ourselves. Maybe some trusted health care organization needs to start a “Go Fund Me”. As G. K. Chesterton observed, there are some things that are too important to be trusted to the state.

7 comments… add one
  • steve Link

    We don’t have enough tests to even do diagnostic testing. When we have enough then go ahead and do what you describe. Trust me, the public health folks would love to do it.

    On the fatality rates we don’t know is correct. It could be a lot lower. It could be higher. W have learned quite a bit from the care they are giving in Italy and China and S Korea, so our care many bye better, if we don’t get overwhelmed. OTOH, we are shorter on supplies. Maybe how we live matters more than we know. We have a pretty high percentage of our elderly in nursing home, assisted living, ad going to day care. Partner’s spouse runs a nursing home and they are terrified of coronavirus.

    What we do know is that we are filling hospitals with patients who need ICU care, ventilators especially, at a rate never seen before. Even if total deaths are down in the flu range, we will have achieved that by needing ICU care for people that would have otherwise died in huge numbers.


  • This is the point that needs consideration:

    What we do know is that we are filling hospitals with patients who need ICU care, ventilators especially, at a rate never seen before. Even if total deaths are down in the flu range, we will have achieved that by needing ICU care for people that would have otherwise died in huge numbers.

    Opinions differ but I strongly suspect that will not be a temporary phase but a permanent fact of life. Some people who might in years past have died of seasonal flu will now die of COVID-19; some additional people will die of COVID-19; things will never really go back to the 2019 normal again.

    I understand your focus on diagnostic testing but I think that the priority should be reversed: epidemiological testing should have the higher priority. Presently, there are all sorts of diseases which are mostly diagnosed not based on tests but on symptoms. I think we will ultimately learn that’s what the South Koreans and Japanese have been doing.

  • steve Link

    “Presently, there are all sorts of diseases which are mostly diagnosed not based on tests but on symptoms.”

    There are a number of problems for which there is no specific test. When there is a specific test, we do it.

    Have already agreed that we should do epidemiological tests, but we still need the diagnostic tests. W are desperately short on PPE gear and finding we are short on other stuff we hadn’t thought about. If someone has a fever, a positive flu test and a negative Covid test that is a lot less PPE gear we can use.


  • Andy Link

    At the very absolute minimum, we need comprehensive diagnostic testing for medical professionals and anyone working with elderly people. We can’t simply assume that the current lockdown on nursing homes and similar facilities will keep the virus out of those populations.

    And we can’t even do that yet. Changing gears to epidemiological testing (and I realize it’s not either/or choice) is premature. We still have many at-risk populations.

  • CStanley Link

    Steve- what’s the feasibility of making the diagnosis based on CT lung scans?

  • steve Link

    CS- Not so good after all. I had initially thought the findings were good enough to be diagnostic but at our big Covid prepare meeting the Radiology chair asked people to stop ordering CT scans as a diagnostic tool as they thought the findings were not specific enough to merit the study. You don’t see the radiologists turning down work too often, so I figure it must be true.


  • steve Link

    Nice link to better/fuller explanation about CT not being useful. Bit of a rant but covers it well.


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