Study Shows ‘Long Flu’ Is Real, but Long COVID Is Worse

Fact checked by Nick Blackmer

Key Takeaways

• People with serious cases of both flu and COVID can experience symptoms throughout their body for months to years after the acute illness has resolved, according to a study.

• People hospitalized with COVID had a greater burden of disease, disability, and death than those with severe flu infections.

• Rather than trivialize a COVID infection by comparing it to flu, experts say that the public should recognize the serious risk of lingering complications of both diseases.

Four years into the COVID-19 pandemic, there’s a general sentiment that COVID has become just like the flu. This raises a question: if some people develop long COVID after the acute infection goes away, do some people experience long-term flu, too?

To compare the long-term consequences of seasonal influenza and COVID, researchers tracked people hospitalized with either illness over 18 months. They found that both illnesses often left people with lingering health problems that can last for months or years.

Influenza has been around for a very long time, but there’s been little attention paid to the symptoms of the illness that linger long after the initial infection is gone, said Ziyad Al-Aly, MD, senior author of the study and a clinical epidemiologist at Washington University in St. Louis.

“The whole narrative is that COVID is like the flu, as if the flu is some benign entity,” Al-Aly said. But the flu kills between 30,000 and 70,000 Americans each year. “Let’s not trivialize this infection,” he added.

Overall, the study participants with long COVID fared worse, with a higher risk of death and likelihood of disability in the long run. People hospitalized with the flu also had long-term, negative health impacts, especially in their lungs and airways.

“My biggest frustration these days is this strange cognitive disconnect where someone will say that now COVID may be similar to influenza in its morbidity and mortality. That is merely to say that now you have at least two really bad viruses, as opposed to saying now we’re okay,” said Marc Sala, MD, a pulmonologist and critical care specialist and co-director of the Northwestern Medicine Comprehensive COVID-19 Center, who wasn't involved with the study.

Related: How Bad Can the Flu Be?

Making Sense of Long Flu and Long COVID

“Long flu,” like long COVID, is a catch-all term used to describe the long-term effects of a flu infection. Al-Aly said this term is rarely used because the long-term outcomes of flu are typically overlooked.

“Because we all lived under the assumption that you get the flu, you get over it,” he said.

The long-term manifestations of the illness tend to come in the form of lingering respiratory problems, like lung fibrosis or shortness of breath.

While the latest research iterates the seriousness of a flu infection, it also indicates that COVID can wreak havoc in the body in even more severe and sustained ways than the flu does.

Related: What Should We Expect From Long COVID Treatment?

The study included more than 81,000 people hospitalized with COVID-19 between 2020 and 2022 and nearly 11,000 with seasonal influenza between 2015 and 2019. Researchers examined 94 potential long-term health outcomes for each disease. People with COVID were more likely to experience 64 of those outcomes, while the flu was associated with six.

Those with COVID had a higher risk of various health complications, such as heart conditions, blood clotting, blood disorders, impaired kidney function, musculoskeletal problems, and neurological effects. The death rate was also greater in the COVID groups.

People hospitalized with COVID were also more likely to experience disability because of their illness—they lost, on average, 2.8 years of healthy life per person.

“To my eyes, studying post-viral complications is more important than ever,” Sala said. “For some reason, we’re seeing more people with long COVID now than we’ve ever seen with people describing long flu historically, and I think it is worth understanding why.”

Unlike the flu, which is a “bona fide respiratory illness,” in Al-Aly’s words, COVID is a multisystemic illness. Though COVID takes hold in and causes harm to the respiratory tract, it tends to affect multiple organ systems throughout the body, especially in its post-acute phase.

Sala said that continuing to categorize COVID as a respiratory disease remains useful for the majority of people who only get mild illnesses.

“I think it’s still very helpful to frame it as a respiratory pathogen, though, simply because that is its mode of transmission and the vast majority of the symptoms in people who don’t have long COVID tend to be sniffles and cough,” he said.

Related: Flu Tests: Who Should Test and When?

Future Research on Long Flu and Long COVID

The new study only focused on people hospitalized with COVID or flu. Sala said that most people experience mild illness, and the findings from this study don’t pertain to them. Besides, as COVID variants evolve, they tend to become more transmissible but less likely to cause people to get really sick.

The researchers could conduct such a large study by using data from the Veterans Health Administration, the largest integrated healthcare system in the U.S. The downside is the demographics of that group: about 95% of the participants in this study were men, and most were White and older.

Al-Aly said the analysis was adjusted for these variables and that VA data has historically been generalizable to the U.S. population. However, Sala said that younger women—the group most likely to experience long COVID—is largely absent from the VA data and ought to be a focus of future research.

The two experts agreed it’s important to continue studying the long-term effects of both diseases in people with mild and severe infections.

“We normalized a lot of risks in this pandemic. We normalized death, disability, and suffering to a very large extent,” Al-Aly said. “I don’t think we should trivialize acute infections and treat them as inconsequential because in some people, they may be actually hugely consequential and leave them with chronic disability and disease.”

Read Next: Long Colds vs. Long COVID: Here's What Researchers Know So Far

What This Means For You

The best way to avoid long flu and long COVID is to get vaccinated for both and to minimize your exposure to people who are sick.

Read the original article on Verywell Health.