2021-10-04 12:34:04 Covid, in Retreat – The New York Times

Covid, in Retreat – The New York Times

Covid-19 is retreating once more.

The reasons are unclear, and there is no guarantee that the caseload decline will continue. However, the turnaround is now large enough — and has been going on long enough — to warrant notice.

Since September 1, the number of new daily cases in the United States has decreased by 35%:

Cases have also decreased by more than 30 percent globally since late August. “This is the best the world has looked in many months,” Scripps Research’s Dr. Eric Topol wrote last week.

These declines are consistent with a pattern familiar to regular readers of this newsletter: Covid’s mysterious two-month cycle. Since the Covid virus began spreading in late 2019, cases have frequently spiked for two months — sometimes due to a variant, such as Delta — and then declined for two months.

Epidemiologists are baffled as to why. Many popular explanations, such as seasonality or the ebbs and flows of social distance, are clearly inadequate, if not incorrect. The two-month cycle has occurred at various times of the year and even when human behavior was not changing in obvious ways.

The most plausible explanations combine virus biology and social networks. Perhaps each virus variant is more likely to infect some people but not others — and once the virus has infected many of the most vulnerable, the virus recedes. And it’s possible that a variant takes about two months to spread through a typical-sized community.

Human behavior does play a role, with people becoming more cautious as caseloads increase. However, social distancing is not as important as public discussion of the virus frequently assumes. According to Michael Osterholm, an infectious-disease expert at the University of Minnesota, “we’ve ascribed far too much human authority over the virus.”

Recent declines, for example, have occurred despite the fact that millions of American children have once again crammed into school buildings.

Hospitalizations, as well.

Whatever the reason, the two-month cycle continues. It can be seen in the global numbers, as shown in the chart below. Cases increased from late February to late April, then decreased until late June, then increased again until late August, and have been declining since.

The pattern has also been observed within countries such as India, Indonesia, Thailand, the United Kingdom, France, and Spain. In each of them, the Delta variant caused a surge in cases that lasted between one and a half and two and a half months.

The Delta surge began in several Southern states in June and began to recede in those states in August in the United States. It began in much of the rest of the United States in July, and cases have started to fall in the last few weeks. Even pediatric cases are decreasing, according to Jennifer Nuzzo of Johns Hopkins University, despite the lack of vaccine authorization for children under the age of 12. (The overall trends for each state can be found here.)

The most heartening news is that serious Covid illnesses are also on the decline. Since September 1, the number of Americans hospitalized with Covid has decreased by about 25%. Daily deaths, which typically change direction a few weeks after cases and hospitalizations, have decreased by 10% since September 20. It’s the first sustained drop in deaths since early summer.

‘The last major tidal wave’?

This is the part of the newsletter where I emphasize that these declines may not be sustained. Covid’s two-month cycle is not some sort of scientific law. There have been numerous exceptions.

In the United Kingdom, for example, caseloads have swung back and forth over the last two months, rather than falling steadily. The onset of cold weather and an increase in indoor activities — or some other unknown factor — could cause an increase in cases this fall in the United States. The pandemic’s path remains highly uncertain.

However, this uncertainty implies that the near future may be more promising than we anticipate. And there are some legitimate reasons to be optimistic about Covid.

The proportion of Americans aged 12 and up who have received at least one vaccine shot has reached 76%, and the growing number of vaccine mandates, combined with the likely approval of the Pfizer vaccine for children ages 5 to 11, will increase the number of vaccinations this fall. Almost as important, roughly one-half of all Americans have probably already been exposed to the Covid virus, providing them with some natural immunity.

Immunity will eventually spread to the point where another wave as large and destructive as the Delta wave will be impossible. “Unless something unexpected happens,” Dr. Scott Gottlieb, a former FDA commissioner and the author of “Uncontrolled Spread,” a new book on Covid, told me, “I believe this is the last major wave of infection.”

Covid was not only one of the worst pandemics in recent history. It was an unnecessarily dreadful pandemic. Nearly 200,000 of the more than 700,000 Americans who have died as a result of it could have been saved if they had chosen to take a vaccine. That is a national calamity.

Covid, on the other hand, is not going away anytime soon. Many scientists believe it will continue to circulate for years. However, vaccines have the potential to turn Covid into a manageable disease, similar to the flu or a common cold. The country appears to have moved closer to that less bleak future in recent weeks.

Whatever this autumn brings, the pandemic’s worst is almost certainly over.

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Covid, in Retreat - The New York Times