Še tretji del zgodbe, ki se nanaša na podobne primere nenadnega drastičnega upada epidemije tudi drugod po svetu. Spodaj je dober povzetek v New York Timesu in pogovor z Michaelom Osterholmom, direktorjem centra za raziskovanje infekcijskih bolezni na University of Minnesota. Njegova razlaga je: ponižnost. Premalo vemo o dinamiki infekcijskih bolezni in morda pripisujemo prevelik pomen človeškim aktivnostim pri omejevanju dinamike epidemije. Kar seveda ne pomeni, da distanciranje, maske in predvsem cepiva nimajo učinka (predvsem slednja so lahko ključ za omilitev posledic epidemij). Velja pa – v luči tega, da tudi najboljši eksperti nimajo odgovora in da poteka epidemije očitno ni mogoče kontrolirati – pretehtati ali so posamezni drastični ukrepi, kot je na primer zaprtje šol in vrcev, smiselno glede na njihove negativne učinke. Sploh pa v luči 4-mesečnega zaprtja Slovenije iz konca lanskega leta, ki na potek epidemije ni imel vidnega učinka.

In še nekaj. Glede na to, da nihče nima dobre razlage glede faktorjev, ki poganjajo ali zavirajo dinamiko epidemije, se morda splača vrniti nazaj k teorijam, ki govorijo o naravnih ciklih epidemij. Kar pa seveda ne pomeni, da kljub naravni dinamiki epidemij ne smemo narediti vsega, kar (smiselno) lahko, da jih omejimo in omejimo njihove posledice za najbolj ranljive skupine.

Consider these Covid-19 mysteries:

• • In India — where the Delta variant was first identified and caused a huge outbreak — cases have plunged over the past two months. A similar drop may now be underway in Britain. There is no clear explanation for these declines.
  • In the U.S., cases started falling rapidly in early January. The decline began before vaccination was widespread and did not follow any evident changes in Americans’ Covid attitudes.
  • In March and April, the Alpha variant helped cause a sharp rise in cases in the upper Midwest and Canada. That outbreak seemed poised to spread to the rest of North America — but did not.
  • This spring, caseloads were not consistently higher in parts of the U.S. that had relaxed masking and social distancing measures (like Florida and Texas) than in regions that remained vigilant.
  • Large parts of Africa and Asia still have not experienced outbreaks as big as those in Europe, North America and South America.

How do we solve these mysteries? Michael Osterholm, who runs an infectious disease research center at the University of Minnesota, suggests that people keep in mind one overriding idea: humility.

Over the course of this pandemic, I have found one of my early assumptions especially hard to shake. It’s one that many other people seem to share — 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.

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Even Osterholm said that he had assumed the spring surge would spread from Michigan and his home state of Minnesota to the entire U.S. It did not. It barely spread to nearby Iowa and Ohio. Whatever the reasons, the pattern shows that the mental model many of us have — in which only human intervention can have a major effect on caseloads — is wrong.

Britain has become another example. The Delta variant is even more contagious than Alpha, and it seemed as though it might infect every unvaccinated British resident after it began spreading in May. Some experts predicted that the number of daily cases would hit 200,000, more than three times the country’s previous peak. Instead, cases peaked — for now — around 47,000, before falling below 30,000 this week.

“The current Delta wave in the U.K. is turning out to be much, much milder than we anticipated,” wrote David Mackie, J.P. Morgan’s chief European economist.

True, you can find plenty of supposed explanations, including the end of the European soccer tournament, the timing of school vacations and Britain’s notoriously late-arriving summer weather, as Mark Landler, The Times’s London bureau chief, has noted. But none of the explanations seem nearly big enough to explain the decline, especially when you consider that India has also experienced a boom and bust in caseloads. India, of course, did not play in Europe’s soccer championship and is not known for cool June weather.

A more plausible explanation appears to be that 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.” The most counterintuitive idea here is that an outbreak can fade even though many people remain vulnerable to Covid.

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.”

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But Osterholm’s plea for humility does have policy implications. It argues for prioritizing vaccination over every other strategy. It also reminds us to avoid believing that we can always know which behaviors create risks.

That lesson has particular relevance to schools. Many of the Covid rules that school districts are enacting seem overly confident about what matters, Osterholm told me. Ventilation seems helpful, and masking children may be. Yet reopening schools unavoidably involves risk. The alternative — months more of lost learning and social isolation — almost certainly involves more risk and greater costs to children. Fortunately, school employees and teenagers can be vaccinated, and severe childhood Covid remains extremely rare.

We are certainly not powerless in the face of Covid. We can reduce its risks, just as we can reduce the risks from driving, biking, swimming and many other everyday activities. But we cannot eliminate them. “We’re not in nearly as much control as we think are,” Osterholm said.

Vir: David Leonhardt, New York Times