The Atlantic – Cases of COVID-19 are rising fast. Vaccine uptake has plateaued. The pandemic will be over one day—but the way there is different now. “This new surge brings a jarring sense of déjà vu. America has fallen prey to many of the same self-destructive but alluring instincts that I identified last year. It went all in on one countermeasure—vaccines—and traded it off against masks and other protective measures. It succumbed to magical thinking by acting as if a variant that had ravaged India would spare a country where half the population still hadn’t been vaccinated. It stumbled into the normality trap, craving a return to the carefree days of 2019; in May, after the CDC ended indoor masking for vaccinated people, President Joe Biden gave a speech that felt like a declaration of victory. Three months later, cases and hospitalizations are rising, indoor masking is back, and schools and universities are opening uneasily—again. “It’s the eighth month of 2021, and I can’t believe we’re still having these conversations,” Jessica Malaty Rivera, an epidemiologist at Boston Children’s Hospital, told me. But something is different now—the virus. “The models in late spring were pretty consistent that we were going to have a ‘normal’ summer,” Samuel Scarpino of the Rockefeller Foundation, who studies infectious-disease dynamics, told me. “Obviously, that’s not where we are.” In part, he says, people underestimated how transmissible Delta is, or what that would mean. The original SARS-CoV-2 virus had a basic reproduction number, or R0, of 2 to 3, meaning that each infected person spreads it to two or three people. Those are average figures: In practice, the virus spread in uneven bursts, with relatively few people infecting large clusters in super-spreading events. But the CDC estimates that Delta’s R0 lies between 5 and 9, which “is shockingly high,” Eleanor Murray, an epidemiologist at Boston University, told me. At that level, “its reliance on super-spreading events basically goes away,” Scarpino said.

In simple terms, many people who caught the original virus didn’t pass it to anyone, but most people who catch Delta create clusters of infection. That partly explains why cases have risen so explosively. It also means that the virus will almost certainly be a permanent part of our lives, even as vaccines blunt its ability to cause death and severe disease…”