In an exchange about coronavirus, homeland security chief gets flu mortality rate wrong

Wolf answered: "It's also right around that percentage as well. I don't have that offhand, but it's right around 2% as well."

We asked the Department of Homeland Security where Wolf's figure came from.

A DHS spokesperson said in an email, "As the acting secretary said in his hearing, he did not have that information on hand and refers to Health and Human Services — the federal agency in charge of the federal government's coronavirus response."

Comparing mortality rates between the coronavirus and flu seemed like an important mechanism for understanding the growing concern about the reach of coronavirus, so we decided to dig deeper to find out if these statistics hold up. We also asked experts to explain what the numbers mean in terms of risk.

Digging into mortality rate numbers

The CDC directed us to its online influenza resources and referred us to the World Health Organization for more information on coronavirus.

Christopher Mores, a global health professor at George Washington University, helped make sense of some figures. He calculated the average, 10-year mortality rate for flu using CDC data and found it was 0.1%. That 0.1% rate is frequently cited among experts, including Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

Dr. Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security, called it "sort of the canonical seasonal influenza mortality figure."

It's important to note that, although this percentage seems like a small number, influenza is responsible for an estimated 30,000 to 40,000 deaths annually.

Now, for coronavirus.

According to statistics released Feb. 17 by the Chinese Center for Disease Control and Prevention, the mortality rate for coronavirus was 2.3%. That's based on cases reported through Feb. 11 and calculated by dividing the numbers of coronavirus-related deaths at the time (1,023) by the number of the confirmed cases (44,672) of the coronavirus.  (These numbers reflect the information available at the time of the secretary's testimony.)

But this report has limitations, Mores said, including the vague way Chinese officials are defining who has been infected by the coronavirus.

"We have not been able to understand what precisely has gone on there," said Mores. "They have changed their case definitions multiple times. It's murky what has gone into the case count and who has gone into being counted on cases."

The WHO said in a press conference Monday that in Wuhan, China, the city where the virus emerged, the mortality rate ranged from 2% to 4%. Officials said that in the rest of China, outside of Wuhan, the mortality rate of coronavirus is 0.7%.

Mike Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the mortality rate in China has since risen to 0.9%.

Right now he doesn't see a similarity in the flu mortality rate and the coronavirus mortality rate. "We don't have any evidence to that being the case," said Osterholm.

Mores said U.S. health officials just don't have enough information to know whether the two mortality rates are similar. Understanding this comparison would offer a means to better understand the severity of the coronavirus. It could also help in educating the public about the novel illness.

"Until we can gain our own experience with this virus, it's going to be pretty squishy. So, all the numbers that you have come across here are within the range of possibility," he said. "Absolutely, the hope is we will end up with something similar to the flu, but we just don't know yet."

Multiple experts told us that the number of coronavirus cases not just in China but worldwide has probably been undercounted because many people with the infection do not suffer serious symptoms and may not seek medical treatment. It is possible that only those who have tested positive are being counted as "confirmed cases."

Until the case definition is expanded to include people clinicians think may have COVID-19 but who were not tested for it, they said, the total estimated number of cases will remain lower than the likely reality. But, if the number of cases widens to include those with mild symptoms who have not been tested, then the mortality rate will go down.

This is the way mortality rates are calculated for the flu, said Mores. The numbers of flu illnesses and deaths are estimates based not only on positive flu tests, but also on doctors' suspicions and symptomatic diagnosis.

One key difference between the flu and the coronavirus illness, Osterholm cautioned, is that, with the flu, the population has a partially built-up immunity, whether through receiving flu shots or already having been exposed to the illness.

Mores concurred. "You know, the risk is this: We have a brand-new virus in a completely naive population on Earth; we're all susceptible to it. Everyone is potentially infectable with this virus," he said. "Even with a high transmission rate and the low case fatality rate, that still becomes a massive number of ill and fatal cases."

Our ruling

There are two ways to parse out this claim: First, is it true that the average U.S. mortality rate for flu is 2%?

That's not true, according to data from the CDC and exchanges with multiple global health experts. On average, the flu mortality rate during the past 10 years has been 0.1%. In addition, Wolf and a DHS spokesperson admitted that the acting secretary did not have the statistics in front of him when he answered questions at the hearing about the mortality rates.

Second, is it true the COVID-19 mortality rate is similar to the flu mortality rate?

Wolf is also wrong on that account, based on the limited information currently known about the coronavirus. Recent data from the Chinese government set the COVID-19 mortality rate at 2.3%. That's vastly different from the flu's mortality rate of 0.1%.

Experts also said that while it's possible the mortality rate from the new virus could come close to the flu's mortality rate eventually - if the case definition of coronavirus were expanded — it's too soon to make that assumption with the limited information available.

For these reasons, we rate the claim False.

Source list:

C-SPAN, "Department of Homeland Security Fiscal Year 2021 Budget Request," Feb. 25, 2020.

The Washington Post, "Trump's DHS head has a brutal exchange on coronavirus — courtesy of a GOP senator," Feb. 25, 2020.

Email exchange with the Department of Homeland Security Office of Public Affairs, Feb. 26, 2020.

Email exchange with the Centers for Disease Control and Prevention Office of the Associate Director for Communications, Feb. 28, 2020.

Centers for Disease Control and Prevention, "Influenza," page last reviewed Jan. 27, 2015.

Centers for Disease Control and Prevention, "Estimated Influenza Illnesses, Medical visits, Hospitalizations, and Deaths in the United States — 2018-2019 influenza season," page last updated Jan. 8, 2020.

Centers for Disease Control and Prevention, "Coronavirus Disease 2019 COVID-19," page last updated Feb. 14, 2020.

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Email exchange with Dr. Amesh Adalja, a senior scholar with the Johns Hopkins University Center for Health Security, Feb. 26, 2020.

Phone interview with Michael Osterholm, Regents professor and director of the Center for Infectious Disease Research and Policy at the University of Minnesota, Feb. 27, 2020.

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