The White House’s favorite new coronavirus metric — mortality rate — probably won’t be a favorite for long

July 13 at 5:12 PM

The first question at Monday’s White House news briefing focused on the coronavirus pandemic.

“As the number of cases and fatalities continues to break records,” CBS News’s Weijia Jiang asked, “in the most recent interview President Trump did, he said, ‘We are going to be in really good shape,’ in the next two to four weeks. Can you share what evidence he’s using to draw that conclusion?”

“The one thing I would note,” White House press secretary Kayleigh McEnany replied, “is that when you look at the mortality rate, we’re seeing that our efforts here at the federal government have been working.” She listed a number of data points, including the number of deaths per 1,000 coronavirus cases in New York and Florida.

Later, she compared the United States’ mortality rate with that of the European Union, where the number of new cases has been pushed down to nearly zero.

“When you compare us to other countries on case fatality rate, other industrialized nations, we’re very low and beating most countries, if not all, in Europe,” McEnany said.

That sort of comparison is precisely why this is the one metric that she would note. It is one metric on which the United States is faring comparatively well — in no small part because we’re in a window where new cases are spiking but the number of deaths accompanying those new cases hasn’t really started to.

Until about a week ago, the divide between those two data points was stark. Since June 9, the number of new cases in the country has been climbing steadily, setting new daily records over and over. Yet the number of deaths from the virus had continued to wane. Why? In part because of improved treatments, as McEnany mentioned — and for which, often without justification, she gave the federal government credit. In part, too, because more younger people are being confirmed to have the virus. And probably in part because more testing has meant catching cases earlier, increasing the time between when infections are logged and when they result in a patient’s death.

As of last Monday, the number of new cases was continually going up as the number of new deaths (recorded as an average of the change over the preceding seven days) was dropping. Over the past seven days, though, the daily number of deaths has started to increase again — inevitably, given all the new cases.

But this also means that the mortality rate — the number of deaths relative to the number of cases — was at its lowest point one week ago. McEnany used the metric of deaths-per-thousand-cases; on that basis, the coronavirus mortality rate in the United States hit a low of 9.2 deaths per 1,000 cases on July 6, the day before the number of deaths began to climb again.

Since the outset of the pandemic, the United States has averaged 40.2 deaths for every 1,000 cases.

But see how that works? The White House seized upon a metric that makes it seem as though it has become particularly effective at keeping people from dying. In reality, this is driven to at least some extent by the necessary gap between when an infection is confirmed and a patient’s death.

It’s not clear what data McEnany was using for her numbers. She presented the number of cases in New York as being 1.7 per 1,000 cases, which is either using week-old data (possible) or confusing the percent of deaths (1.7 per 100, according to Post data) with her cases-per-thousand metric. There’s no way to do a real-time evaluation of the metric precisely because confirmed cases and confirmed deaths correlate on a varying delay. (The government’s data for coronavirus deaths are tallied on a further delay, which has in the past caused some confusion.)

McEnany’s comparison with Europe isn’t wrong. A number of European Union countries (and Britain) have overall mortality rates higher than the United States. But so do a number of U.S. states, including those that recorded a significant number of deaths in March, April and May. The European Union’s mortality rate, like the U.S. rate, is lower than its hardest-hit member states, but higher than the United States.

Comparing the current U.S. mortality rate with that of other countries, though, is dishonest for a slightly different reason. Here, for example, is how the United States compares with Italy both overall and on the most recent seven-day averages of cases and deaths.

Country Overall rate Current rate
U.S. 40.2 per 1,000 cases 12.1
Italy 143.8 62.8

It seems as though we’re doing far better than Italy on that current metric. We aren’t.

Why not? Because Italy has very few new cases and, therefore, very few new deaths.

Ninety percent of Italy’s current total number of cases had been recorded by May 12. By comparison, 90 percent of the United States’s current total wasn’t hit until July 7 — meaning that 1 in 10 cases we’ve seen has been confirmed over the past week or so.

That’s important because it means that Italy’s overall mortality rate was largely locked in by the middle of May, since it has added relatively little to either the numerator or denominator of its equation. Yes, its current mortality rate is 62.8, but on average it’s adding only about 200 cases a day compared with the nearly 60,000 for the United States. With an average 13 deaths, you get a current mortality rate of about 63 per 1,000 cases — five times the United States, where nearly 60 times as many people are dying.

Again, the low mortality rate for the United States is, to some extent, probably a function of our improved ability to treat covid-19, the disease caused by the virus. That’s one reason that so many people died in Italy and New York; we simply knew less about how to effectively treat the virus.

It is also the case that the mortality rate is a convenient metric in this particular moment, before the increase in the number of deaths that accompanies the surge in new cases drives mortality back upward. If the current increase in the seven-day average of new deaths keeps climbing, look for the White House to move this talking point back to the dustbin.

Until then? Well, at an event on Monday afternoon, President Trump was asked whether he acknowledged that the increase in new cases wasn’t solely a function of increased testing.

“Well,” he replied, “you know that we have one of the lowest mortality rates anywhere.”