Patients and nurses in a hospital intensive care unit

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Excess deaths show the true impact of COVID-19 in the U.S.

Epidemiologist Justin Lessler unpacks a recent CDC report on comorbidities and coronavirus deaths that is being misinterpreted on social media

Since COVID-19 first began circulating within the United States, public health officials have known that those with underlying medical conditions face higher risks for severe illness and death if they contract the disease. A recent report from the CDC appears to drill down that point with striking numbers, showing that 94% of U.S. deaths involving COVID-19 since February were also associated with other conditions, or comorbidities.

According to the CDC: "For 6% of [coronavirus disease 2019] deaths, COVID-19 was the only cause mentioned. For deaths with conditions or causes in addition to COVID-19, on average, there were 2.6 additional conditions or causes per death. The number of deaths with each condition or cause is shown for all deaths and by age groups."

The most common comorbidities, according to death records, include influenza and pneumonia, respiratory failure, hypertension, diabetes, and cardiac arrest.

The report has sparked confusion on the topic and some misleading narratives on social media, but Johns Hopkins epidemiologist Justin Lessler emphasizes that these findings are not surprising. COVID-19 deaths are not easy to predict or prevent based on comorbidities, he says, and the virus is not only a concern for those with medical problems.

"[The report] surely includes some new data, but the general finding—that comorbidities increase your risk of dying from COVID-19—is not a surprise at all," Lessler says. "This would be true for the flu or cancer or chicken pox. Really almost any disease you can name, your risks for death increase if you have other diseases and other conditions that make you sick."

Lessler, an infectious disease specialist at the Bloomberg School of Public Health, spoke with the Hub to further clarify the CDC findings and their significance.

Can you break down what the data means?

The importance of this CDC data is showing the comorbidities in people who have died with COVID-19, in hopes of better understanding the risk factors for death. For almost everyone, I think we can be confident they would have lived longer without COVID-19.

But it's important to understand that some of the comorbidities listed are actually downstream effects of COVID-19—meaning they are symptoms. For example, respiratory failure. Someone could have on their death certificate that they died of both COVID and respiratory failure, but that probably means that COVID-19 caused the respiratory failure, which caused them to die. It's impossible for us to know the individual scenarios from death certificates, but the prevalence of respiratory factors [in the CDC findings] are consistent with being downstream conditions.

How do you think some people may be misinterpreting or misunderstanding this?

To some extent I think some people are willfully misinterpreting to treat this as a "gotcha" moment to undermine the seriousness of COVID-19. They're not taking time to actually understand the data.

But I also think there's legitimate confusion, because the general public may be inclined to think of deaths as having one single cause and that's not the way we look at things as epidemiologists and public health people. We think of component causes. So, for example, you can die from drinking too much and heart failure, because drinking led to heart failure. So a table like this listing multiple component causes of death, without individual context, can be confusing.

"Many of the comorbidities in the CDC data could be downstream effects. Just because you don't have respiratory problems now doesn't mean if you get COVID-19 you won't have respiratory problems."
Justin Lessler

Can you explain the "200,000 excess deaths" you referenced in your recent tweet?

We can observe trends from the number of deaths reported each year, on a weekly basis. When we see large deviations in the numbers for a time period, we call that excess deaths. Looking at 2020 since March, the raw number of excess deaths is 200,000 more people than a normal year. When we try to understand that, COVID-19 is the most rational and likely explanation. If you don't believe it's COVID-19, try to pinpoint why this year has been so different than any other. Why would a new disease that kills people not be the cause?

What is the takeaway for people who don't have comorbidities?

If you aren't aware that you have any comorbidities, that doesn't mean you should treat that as carte blanche to go out, get infected, and not worry about consequences. Comorbidities are frequent in the population, particularly in the U.S., where tens of millions of people have heart disease and diabetes and other conditions—and many don't even know it. And again, many of the comorbidities in the CDC data could be downstream effects. Just because you don't have respiratory problems now doesn't mean if you get COVID-19 you won't have respiratory problems.

Certainly if you know you have a comorbidity, that's reason to be extra careful. Or if you have a family member who has a comorbidity, be extra careful when visiting them. But I also want to emphasize that just because some people have more risk factors or presumably less long to live than others doesn't make those deaths any less tragic.