The COVID-19 outbreak is dynamic, hitting some places and some people hard and others less so, then tapering off and sometimes resurging.
To track it, we use data, but even the most robust counts have limitations.
The Oxford-based nonprofit Our World in Data explains the conundrum: “Without data, we can not understand the pandemic. Only based on good data can we know how the disease is spreading, what impact the pandemic has on the lives of people around the world, and whether the countermeasures countries are taking are successful or not.
“But even the best available data on the coronavirus pandemic is far from perfect.”
It may seem obvious that no single graph, figure, or stat is sufficient to give a meaningful picture of the situation, yet some circulate the internet with little explanation, as though they are capable of this.
For example, in early June, some media mentioned, without any explanation or context, the fact that the United States was reporting the highest number of COVID deaths of any country. This fact was true. But without context, one might infer that thus the United States was doing a poorer job handling the crisis.
The first and most obvious mitigating factor is that the United States has a larger population than other developed countries. Those countries closest in population size—India, Pakistan, Indonesia, Nigeria—are third world nations, and thus their governments won’t have the resources to test and track to the same extent as the United States. It’s common sense that we wouldn’t compare the United States to them.
So is it fair if we compare disease rates in other developed countries to the United States? Somewhat, as long as differences in testing and data are taken into consideration.
Media reports in early July compared the number of cases in the United States to the number of cases in the European Union (EU) due to their somewhat comparable population sizes: 328 million in the United States, and 446 million people in the 27 countries of the EU.
The Our World in Data website on July 5 shows that the United States had counted 2.9 million cases of COVID with 132,000 deaths, while the EU reported 1.3 million cases and 134,000 deaths.
Although the United States has reported more than twice as many cases, it has only a slightly higher rate of death, which is the number of deaths compared to the population. Using the population and death statistics above, the rate of death in the United States is 0.04 percent compared to 0.03 percent in the EU.
There are a few factors behind these numbers to consider.
One is who/what is being counted in test numbers. There is no international standard of testing for the pandemic, and different countries are following different methods. Some are counting the number of people tested, while some are counting numbers of tests given. And some countries, as in the case of Italy and France, changed their reporting criteria midway.
A second factor is scale of testing. According to Our World in Data, most EU countries (19) are only testing people with symptoms, while the United States is testing asymptomatic people.
The United States also is testing more aggressively than EU countries. Of the 27 EU countries, only Luxembourg, Denmark, and Portugal have conducted more tests per capita (1,000 persons) than the United States.
More testing will, of course, uncover more cases. In the United States, the number of daily tests given is still rising, whereas the tests in Europe are flat.
Case Fatality Rates Don’t Necessarily Indicate Mortality
Case fatality is the number of known cases compared to the number of known deaths.
A common misconception is that the case fatality rates indicate how severe a disease is. This isn’t necessarily the case.
To give a hypothetical example: If two people come to a hospital with a strange new disease (both somehow test positive) and both then die of the disease, in this sample, the case fatality rate is 100 percent.
So this number is relative to the number of positive tests. In countries where many tests have been conducted, the case fatality rate will be low, such as in the United States.
The case mortality rate in the United States is around 4.6 percent (Johns Hopkins University calculated the U.S. case fatality rate at 4.2 percent on July 12). Case mortality in the EU was 10.3 percent as of July 5.
Mortality Assessment Differences
Then, there’s the criteria for classifying a death as being from COVID-19.
In the first week of April, White House Coronavirus Response Coordinator Dr. Deborah Birx said at a press conference, “I think in this country, we’ve taken a very liberal approach to mortality.”
She said that in other countries, if someone had a preexisting condition and came to the hospital and died of COVID, it might not be counted as a COVID death, while in the United States, it might.
Additionally, deaths classified as COVID-19 in the United States “can include … cases without laboratory confirmation,” according to the Centers for Disease Control and Prevention (CDC).
The CDC acknowledges that this lack of testing will introduce some error for mortality figures for COVID-19, flu and flu-like illnesses, and pneumonia.
“Deaths due to COVID-19 may be misclassified as pneumonia or influenza deaths in the absence of positive test results, and pneumonia or influenza may appear on death certificates as a comorbid condition. Additionally, COVID-19 symptoms can be similar to influenza-like illness, thus deaths may be misclassified as influenza. Thus, increases in pneumonia and influenza deaths may be an indicator of excess COVID-19-related mortality.”
In hard-hit EU countries such as Italy and France, lab confirmation is required.
This article was updated on Aug. 2, 2020, to clarify that the rate of death refers to the number of deaths as a percentage of the total population.