MEGAN BASHAM, HOST: It’s Thursday, October 8th, 2020. You’re listening to The World and Everything in It and we’re so glad you are! Good morning, I’m Megan Basham.
MARY REICHARD, HOST: And I’m Mary Reichard. First up: COVID-19 statistics.
In August, we asked two reporters to dig into some of the most common coronavirus numbers. Data points that you’ve probably heard and scratched your head about. Things like positive case counts, different types of testing, mortality rates, and recoveries.
BASHAM: If you missed it, we will link to it in today’s transcript.
A lot of you wrote to say how much you appreciated that explainer, but you still had a lot of questions. So we put WORLD reporters Anna Johansen and Sarah Schweinsberg back on assignment to find some answers.
MONTAGE: Florida now surpassing 100,000 cases… We are up to 14 million cases globally… There’s been dramatic increase in hospitalizations… The U.S. has now conducted 28 million COVID-19 tests… The United States is reporting the highest number of deaths in a single day—nearly 1,500.
SARAH SCHWEINSBERG, REPORTER: I’m Sarah Schweinsberg.
ANNA JOHANSEN, REPORTER: And I’m Anna Johansen.
JOHANSEN: Pandemic terminology can be a slippery thing. We picked some of it up really fast: Asymptomatic, social distancing, even the word itself—pandemic. When did the average person say “pandemic” pre-2020?
SCHWEINSBERG: Only when I tried playing the board game.
JOHANSEN: But some of the COVID-related words and phrases we hear these days are harder to pin down.
PRINCESS BRIDE: You keep on using that word. I do not think it means what you think it means.
JOHANSEN: Take this term: Fatality rate. There are at least three terms related to COVID-19 fatality that you might have heard used interchangeably: Case fatality rates, infection fatality rates, and mortality rates. They obviously sound similar, but they all measure something different.
SCHWEINSBERG: Let’s start with case fatality rates or CFR. This looks at how many people have died from COVID-19 versus how many people have had COVID-19. In algebra terms: virus deaths divided by confirmed virus cases. That gives you a percentage. Right now, the U.S. case fatality rate is 2.8 percent. That means of all the people who have tested positive for COVID-19, 2.8 percent of them have died.
JOHANSEN: Case fatality rates vary widely by country and it’s tough to tell how reliable they are because the ratio depends on a nation’s ability to test for the virus—something that’s easier to do in developed countries.
SCHWEINSBERG: The infection fatality rate or IFR tries to cast a wider net. Here’s Dr. Amesh Adalja. He’s a senior scholar at the Johns Hopkins University Center for Health Security.
ADALJA: What we really want to know eventually is the intrinsic fatality rate, what inherent risk of death is there for being infected, and that’s the infection fatality rate.
SCHWEINSBERG: The IFR is the proportion of virus deaths to COVID-19 cases. Notice I didn’t say confirmed COVID-19 cases. Researchers think anywhere from 40 to 80 percent of everyone who has COVID-19 is asymptomatic. If the majority of people don’t show any signs of the virus, that means there’s a good chance they’ll never get tested and become a confirmed virus case.
JOHANSEN: Chris Lindsell is a biostatistician at Vanderbilt University. He says without the ability to test huge numbers of people in order to catch all of the asymptomatic cases, it’s difficult to calculate a true infection fatality rate and get a precise picture of the virus.
LINDSELL: There are many statistical models that provide an estimate. The fact that they’re not all the same, and they don’t give you all the same answer should be meaningful. It means that the actual, the precise truth is difficult to get our hands around. And it’s also one of the biggest reasons why we are struggling so much with understanding the pandemic.
SCHWEINSBERG: In the meantime, biostatisticians have to rely on projections and estimates to calculate the IFR. The total U.S. infection fatality rate estimates range from .5 percent to .8 percent. That’s anywhere from 1-and-a-half to 2-and-a-half million Americans.
JOHANSEN: That’s significantly lower than the current case fatality rate of 2.8 percent, which comes out to 9 million people. But as testing increases, those numbers should start to align. Here’s Dr. Adalja.
ADALJA: You get what’s called the severity bias in the data, where the CFR is likely higher than the true IFR. Because you’re missing so many cases because you don’t have the diagnostic testing capacity. And as you get better at diagnosing, you will see the two numbers approach each other.
SCHWEINSBERG: And last, we have the mortality rate. This just divides the total number of confirmed COVID-19 deaths by the entire population. Infected and uninfected. The U.S. mortality rate is .06 percent.
Jose Miguel Yamal is a biostatistician and data scientist at the University of Texas. He says this is the least helpful measurement.
YAMAL: So mortality rates is not taking into account whether, you know, the whole population has been infected, which no population, yet has gotten to that level.
JOHANSEN: So the case fatality rates and infection fatality rates measure all cases across all age groups. But when it comes to COVID-19, your chances of dying really depend on how old you are and your underlying health issues.
SCHWEINSBERG: That’s right. The infection fatality rates vary widely by age groups. Here are the CDC’s latest numbers. If you are 19-years-old or younger, you have a .003 percent chance of dying from the coronavirus.
JOHANSEN: If you are between 20 and 49 years old, your odds jump to .02 percent. For ages 50 to 69, the IFR climbs again to .5 percent. Anyone older than 70 has the biggest risk by far—a 5.4 percent chance of dying from COVID-19.
SCHWEINSBERG: So it’s important to look at what kind of group you have, because it will affect your statistics and how dangerous the virus appears. For example, in Italy, the population is much older—the second highest in the world. Having a more vulnerable population overall drove up its case fatality rates to 7.2 percent in March, nearly 5 percentage points higher than the United States.
JOHANSEN: Now, depending on who you are and how old you are, you may be thinking all of these death rates either sound really serious or not something to worry about. So is there a way we can put these numbers into context? Can we maybe compare COVID-19 to other diseases?
We asked five biostatisticians and epidemiologists about this, and all of them said no, not really.
Here’s Chris Lindsell at Vanderbilt.
LINDSELL: It is not the same as the flu virus. It is not the same as the common cold. It is not the same as the Ebola virus. It is a virus in and of itself. It’s its own thing.
SCHWEINSBERG: COVID-19 is most often compared to the flu. But the experts we spoke with said that comparison is difficult to make simply because of how long we’ve known about the flu. Humans have battled influenza for centuries. That means we’ve built up more immunity, a vaccine, and knowledge about how to protect ourselves. Which means juxtaposing the flu and COVID-19 isn’t really a fair comparison. Because we just don’t have that information yet.
JOHANSEN: One difference between the flu and COVID-19 is which demographics are affected most. Jennifer Nuzzo is the lead epidemiologist for the Johns Hopkins Covid-19 Testing Insights Initiative.
NUZZO: Seasonal flu, what we deal with every year, tends to hit the very young and the very old. This virus is particularly hard on the very old. Fortunately, children aren’t, don’t seem to be as hard hit by this virus as they can be with flu.
SCHWEINSBERG: Here’s another difference: So far, Dr. Amesh Adalja says the COVID-19 infection fatality rate is higher than the flu.
ADALJA: I would not compare this to the ordinary seasonal influenza. I would not compare this to the 2009 H1N1 pandemic because it is more severe than both of those. It probably has a true IFR or CFR however you want to say it, six times or so worse than the seasonal flu.
JOHANSEN: It seems like the CDC or the World Health Organization are always releasing updates about what we know—or don’t know—about the virus. And sometimes those numbers can look contradictory.
SCHWEINSBERG: We wanted to ask some data gurus about a new number that the Centers for Disease Control and Prevention issued in August. You might have seen this going around on social media. The CDC report said that 94 percent of COVID deaths had contributing factors; only 6 percent died of COVID alone.
JOHANSEN: Here’s what happened. The CDC did not change the official number of Americans who died after testing positive for COVID-19. It clarified information about the causes of death. The report said that less than 10,000 people in the United States had died of only COVID-19. The rest also had two or three other contributing factors. Dr. Amesh Adalja says that isn’t surprising.
ADALJA: You have to remember that COVID-19 does accelerate and accentuate other other medical conditions, like cardiovascular disease, like strokes, like pulmonary embolisms, or blood clots in the lungs, and people would not have died, were it not for COVID-19. And we’ve known from the beginning, that high risk groups, people who have other comorbid conditions are going to be the ones that are most likely to die. And I think that’s what the data reflects.
SCHWEINSBERG: So how should that clarified information shape our perception of the virus?
Jennifer Nuzzo at Johns Hopkins says it should be a red flag for people with other health problems and their family members and friends.
NUZZO: What that clarification means is that if you have an underlying health condition, you should be particularly concerned about your risk of dying, were you to contract the virus.
JOHANSEN: But it does raise questions about the response to the virus. Because that response also has an impact on all demographics. Jose Miguel Yamal at the University of Texas points out some deaths have decreased because of the response to COVID-19…
YAMAL: For example, traumatic brain injuries, you know, with people staying at home more and taking less risky behavior, that there’s been a lot less traumatic brain injuries.
…but others have increased.
YAMAL: And there’s also other issues like deaths due to food insecurity, and mental health. And those other factors may be due to the pandemic itself, but not specifically to the virus. And so the situation is, is mixed, and it’s complicated.
SCHWEINSBERG: Remember last time, when we talked about excess mortality? That’s the difference between the actual number of deaths in a time period and the expected number of deaths in the same time period.
For example, The New York Times reported that between March and May, New York and New Jersey had more than 44,000 excess deaths. Two-thirds of those people died from COVID-19, but the others died from heart disease, Alzheimers, and influenza. Those people may have chosen to stay away from hospitals because they didn’t want to risk exposure to COVID-19.
JOHANSEN: There are plenty of other questions still to answer. That’s true for the experts, too! There are still many things statisticians, epidemiologists, and public health experts don’t know about this virus or what the response to it means for the lives of billions of people. And that’s a difficult tension for them—and all of us—to live in.
Reporting for WORLD, I’m Anna Johansen.
SCHWEINSBERG: And I’m Sarah Schweinsberg.