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CDC Misleads: Calls .01 Percent Chance of Infection, ‘Less Than 10 Percent’

People walk under cherry blossom trees at Battersea Park in London, England March 23, 2021. (Hannah McKay/Reuters)

The CDC has published a technically true — but profoundly misleading — statistic about the chance of outdoor infection. The story is brought to us by New York Times journalist David Leonhardt in his daily, “The Morning Newsletter”:

When the Centers for Disease Control and Prevention released new guidelines last month for mask wearing, it announced that “less than 10 percent” of Covid-19 transmission was occurring outdoors. Media organizations repeated the statistic, and it quickly became a standard description of the frequency of outdoor transmission.

So, what’s the actual number?

The number is almost certainly misleading. It appears to be based partly on a misclassification of some Covid transmission that actually took place in enclosed spaces (as I explain below). An even bigger issue is the extreme caution of C.D.C. officials, who picked a benchmark — 10 percent — so high that nobody could reasonably dispute it.

That benchmark “seems to be a huge exaggeration,” as Dr. Muge Cevik, a virologist at the University of St. Andrews, said. In truth, the share of transmission that has occurred outdoors seems to be below 1 percent and may be below 0.1 percent, multiple epidemiologists told me.

That is not merely an exaggeration. It’s what is known as a whopper.

Leonhardt makes an apt point:

Saying that less than 10 percent of Covid transmission occurs outdoors is akin to saying that sharks attack fewer than 20,000 swimmers a year. (The actual worldwide number is around 150.) It’s both true and deceiving.

He also takes a generous view of the CDC’s motivation:

This isn’t just a gotcha math issue. It is an example of how the C.D.C. is struggling to communicate effectively, and leaving many people confused about what’s truly risky. C.D.C. officials have placed such a high priority on caution that many Americans are bewildered by the agency’s long list of recommendations. Zeynep Tufekci of the University of North Carolina, writing in The Atlantic, called those recommendations “simultaneously too timid and too complicated.

Let’s assume that Leonhardt’s analysis of this profound and intentional inaccuracy as simple, good-faith, precautionary-principle self-protection — rather than making risk appear greater than it actually is toward the end of accruing power in the technocracy — is right. It doesn’t matter.

Vastly overstating the risk of COVID transmission outdoors causes profound societal harm. As Leonhardt writes:

Erring on the side of protection — by exaggerating the risks of outdoor transmission — may seem to have few downsides. But it has contributed to widespread public confusion about what really matters. Some Americans are ignoring the C.D.C.’s elaborate guidelines and ditching their masks, even indoors, while others continue to harass people who walk around outdoors without a mask.

All the while, the scientific evidence points to a conclusion that is much simpler than the C.D.C.’s message: Masks make a huge difference indoors and rarely matter outdoors.

“Follow the science” requires that the people can safely trust that “the scientists” will communicate facts accurately. The CDC has failed in this basic task abysmally.

Thanks to David Leonhardt for setting the record straight. The CDC should revise its communication accordingly.

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