The Atlantic - July 9, 2020

For the past few weeks, I have been obsessed with a mystery emerging in the national COVID-19 data.

Cases have soared to terrifying levels since June. Yesterday, the U.S. had 62,000 confirmed cases, an all-time high—and about five times more than the entire continent of Europe. Several U.S. states, including Arizona and Florida, currently have more confirmed cases per capita than any other country in the world.

But average daily deaths are down 75 percent from their April peak. Despite higher death counts on Tuesday and Wednesday, the weekly average has largely plateaued in the past two weeks.The gap between spiking cases and falling-then-flatlining deaths has become the latest partisan flashpoint. President Donald Trump has brushed off the coronavirus surge by emphasizing the lower death rate, saying that “99 percent of [COVID-19 cases] are totally harmless.” On Tuesday, Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, warned Americans against “[taking] comfort in the lower rate of death” just hours before Trump tweeted triumphantly: “Death Rate from Coronavirus is down tenfold!”

Read: All the president’s lies about the coronavirus

In the fog of pandemic, every statistic tells a story, but no one statistic tells the whole truth. Conservatives seeking refuge in today’s death counts may find, in a matter of days, that deaths are clearly resurging and their narrative is rapidly deteriorating. But liberals, too, should avoid the temptation to flatly reject any remotely positive finding, for fear that it will give succor to the president.

What follows are five possible explanations for the case-death gap. Take them as complementary, rather than competing, theories.

1. Deaths lag cases—and that might explain almost everything.

You can’t have a serious discussion about case and death numbers without noting that people die of diseases after they get sick. It follows that there should be a lag between a surge in cases and a surge in deaths. More subtly, there can also be a lag between the date a person dies and the date the death certificate is issued, and another lag before that death is reported to the state and the federal government. As this chart from the COVID Tracking Project shows, the official reporting of a COVID-19 death can lag COVID-19 exposure by up to a month. This suggests that the surge in deaths is coming.

In Arizona, Florida, and Texas, the death surge is already happening. Since June 7, the seven-day average of deaths in those hot-spot states has increased 69 percent, according to the COVID Tracking Project.

The death lag is probably the most important thing to understand in evaluating the case-death gap. But it doesn’t explain everything. Even where deaths are rising, corresponding cases are rising notably faster.

2. Expanded testing is finding more cases, milder cases, and earlier cases.

There is a bad way to talk about testing, and a nuanced way to talk about it.

The simplistic version, which we often hear from the president, is that cases are surging only because the number of tests is rising. That’s just wrong. Since the beginning of June, the share of COVID-19 tests that have come back positive has increased from 4.5 percent to 8 percent. Hospitalizations are skyrocketing across the South and West. Those are clear signs of an underlying outbreak.

Something subtler is happening. The huge increase in testing is an unalloyed good, but it might be tricking us with some confusing weeks of data.

In March and April, tests were scarce, and medical providers had to ration tests for the sickest patients. Now that testing has expanded into communities across the U.S., the results might be picking up milder, or even asymptomatic, cases of COVID-19.

Read: A dire warning from COVID-19 test providers

The whole point of testing is to find cases, trace the patients’ close contacts, and isolate the sick. But our superior testing capacity makes it difficult to do apples-to-apples comparisons with the initial surge; it’s like trying to compare the height of two mountains when one of the peaks is obscured by clouds. The epidemiologist Ellie Murray has also cautioned that identifying new fatal cases of COVID-19 earlier in the victims’ disease process could mean a longer lag between detection and death. This phenomenon, known as “lead time bias,” might be telling us that a big death surge is coming. ...
Read full report with chart and graph at The Atlantic