The ebb and flow of a pandemic cannot be explained by changes in human behavior

In one of his morning newsletters for the New York Times last week, David Leonhardt had a piece headlined “Not in Control,” in which he asks readers to consider a slew of “COVID-19 mysteries.” Almost all of them involve instances in which the original virus or variants were expected to spread but didn’t, with no reasonable explanation.

In India, for example, where the Delta variant was first identified and caused a major outbreak, cases have dropped precipitously in the past two months. In the US, meanwhile, a rapid drop began in January before vaccination was even widespread nationally. In March and April, the Alpha variant caused a spike in cases in the upper Midwest and Canada, but inexplicably, it never spread to the rest of North America. And in Africa and Asia, large parts of those continents still haven’t had outbreaks on the level of the ones Europe, North America, and South America have experienced.

Leonhardt spoke with Michael Osterholm, director of the infectious disease research center at the University of Minnesota, who “suggests that people keep in mind one overriding idea: humility.” As Dr. Osterholm put it, “We’ve ascribed far too much human authority over the virus.”

Reflecting on what he has learned from these unexplained, albeit happy failures of the virus to spread, Leonhardt writes that

I have found one of my early assumptions especially hard to shake…  namely, that a virus always keeps spreading, eventually infecting almost the entire population, unless human beings take actions to stop it. And this idea does have crucial aspects of truth. Social distancing and especially vaccination can save lives.

But much of the ebb and flow of a pandemic cannot be explained by changes in human behavior. That was true with influenza a century ago, and it is true with Covid now. An outbreak often fizzles mysteriously, like a forest fire that fails to jump from one patch of trees to another.

This has been true even regarding the current major source of worry, the Delta variant. On the one hand, an internal Centers for Disease Control and Prevention document presents data from which it appears that Delta causes more severe illness than earlier variants and spreads as easily as chickenpox.

Yet, when the variant began spreading in Britain in May, some experts predicted that the number of daily cases would explode. Instead, according to David Mackie, J.P. Morgan’s chief European economist, “The current Delta wave in the UK is turning out to be much, much milder than we anticipated.” Leonhardt writes that there are many “supposed explanations” for what has — or more accurately, hasn’t — happened in Britain, but none that are as plausible as this one:

“Delta spreads very quickly at first and, for some unknown set of reasons, peters out long before a society has reached herd immunity. As Andy Slavitt, a former Covid adviser to President Biden, told me, ‘It seems to rip through really fast and infect the people it’s going to infect.’”

That’s not guaranteed to happen everywhere, and there probably will be more variants after Delta. Remember: Covid behaves in mysterious ways. But Americans should not assume that Delta is destined to cause months of rising caseloads. Nor should they assume that a sudden decline, if one starts this summer, fits a tidy narrative that attributes the turnaround to rising vaccination and mask wearing. ‘These surges have little to do with what humans do,’ Osterholm argues. ‘Only recently, with vaccines, have we begun to have a real impact.’

The inability to explain COVID-19’s imponderables is nothing new. Last year, even as we were in the thick of lockdowns, the spread of the pandemic had already been wildly uneven. Africa, for example, with a population of 1.3 billion, had at that point seen fewer than 50,000 COVID-19 cases and fewer than 2,000 deaths, or two deaths per million people, compared to nearly 200 per million in Europe.

At the time, I offered my own still-enduring hypothesis, whose beauty lies in its simplicity and comprehensiveness, its ability to account for and makes sense all of the contradictory evidence from different countries and regions.

Perhaps, I posited, the enigmatic aspects of the virus are not a bug, but a feature, whose purpose is to make clear that all the theories are ultimately inadequate. And that ought to impel us to do what the entire crisis is designed to do in the first place — to recognize what — Who — brought it all about.

And in acknowledging that “we’re not in nearly as much control as we think are,” Dr. Osterholm is more than halfway there.

(Originally featured in Mishpacha, Issue 872)