When doctors meet a patient for a new complaint, we make a list of different possible explanations for the problem—a differential diagnosis—and try to determine the correct diagnosis, while starting treatment for the most likely one. After this initial assessment, as test and imaging results come in, we may alter the differential diagnosis and treatments.
Public-health officials dealing with a new pathogen, like the coronavirus that causes Covid-19, go through a similar process. They must recommend policies with incomplete information and adjust them over time. But unlike physicians, they do so in public, and sometimes under intense scrutiny.
Dr. Anthony Fauci—and this is not meant as criticism—has epitomized the public-health diagnostic process with multiple, incorrect, early pronouncements: In January and February, he downplayed the risk of person-to-person spread; he expressed doubt that asymptomatic people could transmit the virus; in late February, he reassured the public that, “at this moment, there is no need to change anything that you’re doing on a day-by-day basis”; and in March, like many other public-health officials here and abroad, he said that, outside of health-care personnel, ordinary people should not wear masks. In fact, both Fauci and Surgeon General Jerome Adams suggested that mask-wearing could increase a person’s risk of being infected. All these assertions proved wrong.
We know a lot more about the virus—how it’s transmitted and how to treat it—than we did a few months ago. For instance, the coronavirus can spread person-to-person from both symptomatic and asymptomatic people. Dr. Fauci now espouses the opposite of each of his earlier statements, but there is nothing wrong with that. As economist John Maynard Keynes purportedly said, “When the facts change, I change my mind—what do you do, sir?”
The lesson: in evolving public-health emergencies—despite the demand from some politicians to “Listen to the science!”—science alone can’t always determine the best course of action. Policymakers have to balance multiple, competing factors while working with imperfect information and uncertain science. In a pandemic, infectious-disease experts can advise that shutting down the economy will limit the spread of deadly disease. But experts from other fields might warn that the same action will also throw millions out of work and lead to increased deaths of people unable or unwilling to obtain medical care for emergencies and chronic diseases, more suicides, and more drug and alcohol abuse.
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