When Will the Delta Surge End?

6 min read
The United States has entered the fourth wave of the pandemic — or fifth, depending on which expert you ask. As the vaccination campaign lags and the...
Workers sanitize a COVID-19 field clinic in the parking garage of the University of Mississippi Medical Center in Jackson, Miss., Aug. 13, 2021. (Rory Doyle/The New York Times)

contagious delta variant spreads, cases and hospitalizations are at their highest since last winter. COVID-19 deaths, too, are on a steady incline.

After every other peak has come a trough, however, often for reasons that were not immediately obvious. In Britain, where the variant is also the dominant form of the coronavirus, daily cases fell from a peak of 60,000 in mid-July to half that within two weeks, though they have since been climbing again.

In India, the numbers spiked to more than 400,000 daily cases this spring; experts estimated that the true figure could be more than 20 times greater. The unimaginable toll shocked many who had declared that the country had successfully eluded the virus. But then, in June, infections fell drastically.

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Scientists are struggling to understand why delta outbreaks in those countries dissipated, even if temporarily, and what that may mean for similar surges, including the one in the U.S.

In the U.S., the variant's pace has slowed, and new infections are falling in some states, like Missouri, that delta struck hard. The number of infections over the last week is now 14% higher than it was two weeks ago, a fraction of the rate during much of July and early August.

Is the delta surge beginning to slow in the U.S.? Or is the variant putting the country on course for months of bumps and valleys?

Expert opinion varies widely on the direction of the virus in the coming months. A number of national forecasts being tracked by the Centers for Disease Control and Prevention predict that cases will rise in the early weeks of September — but many foresee the opposite.

"Whatever downturn we have, I think, will be fairly mild," said Dr. Celine Gounder, an epidemiologist and infectious disease…
Apoorva Mandavilli
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