Why reporting *estimated* COVID-19 infections rather than just confirmed cases might save lives

Day after day we see startling and quickly rising numbers of confirmed COVID-19 infections. They’re scary. But the true scope of the pandemic is almost certainly scarier.

Confirmed cases represent only a fraction of the real spread. In most communities, only the sickest patients are being tested so most people with mild symptoms and those that are asymptomatic go untested and unreported. The real number of people who have been infected by the virus almost certainly dwarfs the cases we know about.

And the public winds up with a distorted picture of how prevalent the virus is, often tragically.

Take the Skagit Valley Chorale that met on March 6th in Washington State. The virus was already killing people an hour away in Seattle but, because there were no reported cases at that time in Skagit county, and there were no estimates of unreported cases publicly available, choir members were convinced it was okay to go ahead with a scheduled rehearsal.

It wasn’t.

Somebody did have an undetected case; likely someone who was not yet symptomatic. Now, of the sixty singers who showed up, two are dead, three others have been hospitalized, and forty-five are sick.

Tragedies like the one unfolding in Skagit County might have been avoided if federal authorities or the major media outlets had instead published estimates of how many undetected cases there were likely to be. Proper estimates would factor in not just what had been confirmed in Skagit Country but, also, cases that had yet to be detected, using confirmed cases in adjacent areas (which locals might have had contact with), and estimates of the rate at which infection spreads. Instead of erroneously assuming that there zero cases in their area, the group might have realized that the probability someone in the choir had already been exposed to COVID-19 was already substantial.

With better information, the event might have been canceled. Instead, the rehearsal became a super spreader event.

Unfortunately, we are inundated many times a day with fresh updates of confirmed cases. Rarely, if ever, do the media or world leaders report forecasts of how broad the real scope is likely to be.

The reality is this: In the United States just over 1.35 million tests had been performed as of April 3rd, which amounts to about .3% of the population being tested. Even if only 1% of the population has been infected, that would mean we have missed three million cases; and it could easily be more. The lack of clarity is a huge problem, because failing to appreciate how many undetected cases there are has likely led many people — including world leaders — to be slow to take the pandemic seriously.

People can’t be expected to make good decisions about their personal safety, and our collective well-being, when the reported numbers are such a small fraction of the real numbers. The minimum requirement for anyone to make good decisions about risk is accurate information on which to base those decisions. And accurate estimates matter even more for a virus with a long delay in symptom onset and apparent asymptomatic spread.

We can’t just look at someone and tell whether they are sick, which is why people rely on the reporting in the first place. The focus on confirmed cases is systematically leading people to underappreciate the magnitude of the problem.

The super spreader event in Skagit is, unfortunately, just one of many. This past week the New York Times reported a similar story of a funeral in Albany, GA. On February, 29th, over 200 people came to mourn Andrew Jerome Mitchell. At the time, there were no known cases in the town but the night of the funeral, a man who had attended was admitted to the hospital with pulmonary distress. Ten days later he tested positive for covid-19. Three days later he died.

As of March 30th, twenty-four other mourners had also died with six more deaths still under investigation. Now there are over 600 confirmed cases in the 90,000 person county and the actual spread of the virus in the county is certainly much higher. The hospitals are overwhelmed and the national Guard has been deployed.

They thought they were safe. They were not.

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Study after study in the cognitive psychology literature shows that people have trouble thinking probabilistically. It’s also clear that many people have been having trouble understanding exponential explosions. When there is exponential growth, every unreported case matters even more, as a handful cases can quickly grow to thousands within a few weeks.

And it’s doubtful that most people recognize how seriously confirmed cases underreport the real situation.

Knowing that there are ten confirmed cases in your neighborhood now doesn’t mean there are only ten cases that you can come in contact with. The reality could well be that there are actually a hundred cases, ten that were tested and confirmed, fifty that have not yet shown symptoms and not yet been tested, another forty that have been tested and still are waiting on their results. In just a few days, that total could as much as double, depending on the county you live in, because of the speed at which the disease tends to spread. (Right now, the number of confirmed cases in New York city is doubling every two and a half days).

Armed with estimates of the actual scope of the problem from expert epidemiologists, far fewer people would engage in unsafe behavior. If this more useful information were being reported, the beaches during spring break might have been emptier.

We can’t get past this until we have had stringent lockdowns for long enough for our healthcare workers to catch up. And we can’t expect citizens to respect stringent lockdown orders unless they have clear and accurate information, not just the data that are most conveniently available. That means getting accurate estimates out is critical.

We urge governments and epidemiologists to start publishing estimates of current cases, which would include both confirmed and not yet discovered infections, and we urge the media to start asking for them–and reporting them, daily. Some of the groundwork is already in place in models that project deaths based on factors such as population density, current testing capacities and methodologies, false negative rates, death rates (and criteria for reporting them), and mitigation strategies. By deriving estimates of currentcases from these models and making those estimates more explicit, and widely available, we can help people and governments make better decisions. No one single estimate will be perfect, but without any readily available sources, we are running almost entirely blind.

At some point, these sorts of estimates will be widely reported, a kind of weather report for the new era. Eventually, universal, regular testing will make those estimates obsolete. Until then, everyone must assume the scope of the spread is vastly bigger than what’s being reported. The best thing that you can do is to act as if everyone you come in contact with is a carrier. Stay inside as much as you possibly can.

Until we have better information, it’s the only safe option.

Annie Duke is author of Thinking in Bets, and co-founder of The Alliance for Decision Education

Gary Marcus, PhD, is a scientist and entrepreneur, and Professor Emeritus at New York University; @garymarcus on Twitter.