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No Testing is not Cause for Optimism

Two readings and a thought related to covid-19 testing.

Lack of information requires us to believe two contradictory things at once. From a policy point of view, we need to understand that very few people are infected yet. And from a personal behavior point of view, we need to understand that many people are already infected.

Policy first. Some people think that the lack of testing means that there could be far more asymptomatic cases than we know, and therefore the disease could far less deadly than we imagine.

But consider the case of the town of Vò, near the epicenter of the Italian outbreak, where all 3000 residents were tested. As severe as the outbreak is in Italy, it corresponded to less then 3% of the population being infected. So as bad as the Italian case is, at least in the one town that was tested, it could be 30 times worse. Blindness is not cause for optimism.

Which individuals should be tested? The right behavior is to do the things that maximize lives saved. That means testing should be done in situations where it would change care, for example on on healthcare providers who do not have the option to isolate, so that they do not inadvertently spread it to other providers and patients.

But of course that means many infected people will be untested, so everybody needs to operate under the assumption that we are all infected.

Paradoxically this lack of information means we need to keep in mind two different realities at once. First, we need to recognize that almost nobody has it yet, so the society-wide damage can and will get far far worse; and second, that we and others are likely to have it, so our personal risk and responsibility is very high. We need to isolate.

The parable of two realities corresponds to the logarithmic and linear view of the disaster. I have posted an updated version of the covid-19 time series tracker, which provides both views on covid19chart.org.

Posted by David at March 23, 2020 01:45 PM