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Protect Yourself From Deadly Flu Complications

How influenza can become life-threatening and what to do to protect yourself


spinner image doctor examines a seriously ill patient in an hospital bed
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Last year’s flu season was one of the lightest on record — a rare silver lining of the COVID-19 pandemic. But the 2021-2022 season could be a doozy, especially for older adults — who are more prone to flu and its complications. “This year, schools and businesses are open and people are out and about, and not all are following mask guidelines,” says Joseph Gastaldo, M.D., system head of infectious diseases at OhioHealth, a health care system in central Ohio. 

Depending on the severity of the flu season, between 750,000 to 1 million people are hospitalized each flu season in the U.S., and 30,000 to 80,000 people die from it, notes Ryan Oyer, M.D., an infectious disease specialist for Kaiser Permanente in Denver. According to the Centers for Disease Control and Prevention (CDC), about 90 percent of these deaths and 50 to 70 percent of flu-related hospitalizations occur among people 65 and older. 

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How sick becomes sicker

Influenza itself can be deadly in vulnerable patients due to difficulties in breathing and dehydration. But complications like pneumonia are the real killers.

It starts with inflammation. “Influenza sets up an inflammatory response in the body, to fight off the infection,” says William Schaffner, M.D., professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center and medical director of the National Foundation for Infectious Diseases. That causes the aches, pains and respiratory distress that make you feel like you’ve actually been in battle.

The flu virus also attaches to — and infects — the cells lining the mucous membranes in the back of the throat, nose and bronchial tubes, Schaffner explains. Normally, these cells eject infectious agents out of the body through the nose or mouth, or they are swallowed. But when impaired by the flu, they allow the bacteria to slip down into the bronchial tubes and trigger a secondary infection in the lungs.

Unfortunately, lying in bed makes people, especially frailer folks, more susceptible to pneumonia. “We don’t cough as vigorously when we do that,” Schaffner notes. “We don’t clear our secretions as well when we’re lying down.”

And things can get worse from there. Once infection sets in, the bacteria can clog up the air sacs in the lungs. That not only makes it hard to breathe but can allow bacteria to escape into the bloodstream, causing an infection called sepsis and, ultimately, leading to organ failure. 

“When that happens in people of advanced age or who have underlying illnesses, you have fatality rates that can be somewhere between 10 and 20 percent, despite the fact that we have good antibiotics,” Schaffner says.

Even after you recover from the flu, you may not be out of the woods. Inflammation related to the disease can also affect various organ systems independently, similar to the way experts have seen long-haul symptoms linger in COVID-19 patients for weeks or months. 

“The inflammatory response continues for a period of time,” Schaffner says. It can involve the blood vessels that feed the heart, increasing the risk of heart attack and stroke for weeks or months. In rare cases, the blood vessels feeding the brain may be affected, triggering encephalitis.

Know your risk factors for severe flu 

Age plays a big role in determining who gets sick and how ill they become. “As you age, your immune system ages, too,” OhioHealth’s Gastaldo says. “As you get older, your recovery rate and your body’s ability to heal itself is slower and not as robust as it is when you’re in your 20s and 30s.”

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Older people are generally less likely to spike a fever, a sign that the body is mounting an immune response. What’s more, vaccines don’t work as well as you age. And seniors are more likely to have other illnesses, such as chronic obstructive pulmonary disease, heart disease, obesity and diabetes, which worsen the flu and its repercussions.

The strain of flu virus also influences the seriousness of illness. Kaiser Permanente’s Oyer says there are generally two major types that circulate in the U.S. — influenza A and influenza B. Influenza A viruses (which are further categorized into strains such as H3N2 and H1N1) tend to cause more severe illness. 

But not all influenza A viruses cause the same severity of sickness. H3N2 viruses tend to be more aggressive than the H1N1 variety, Oyer says, but this is not always true. “The 1918 Spanish flu killed 50 to 100 million people, and it was an H1N1 virus,” he says. “Generally speaking, however, we expect that in years in which influenza-A H3N2 viruses predominate, there will be more complications and hospitalizations than years when influenza-A H1N1 or influenza B viruses predominate.”

How to protect yourself

If you think you’re coming down with the flu, experts advise seeking medical treatment immediately.

Editor’s note: This article was updated in September 2021 with new information about the 2021-2022 flu season.

When to go to the hospital

The flu can make you feel miserable and weak. But how do you know you’ve made a turn for the worse and need help — stat?! 

Being short of breath after little or no exertion is one red flag. “Struggling to breathe when you’re eating or finding it hard to have a normal conversation because you’re short-winded — those are clues that you need to seek help,” says OhioHealth’s Joseph Gastaldo, M.D. 

The same goes for uncontrolled fever, especially if it disappears but later returns. “Fever is potentially dangerous in older people,” Gastaldo says. That’s because it leads to sweating and dehydration, which can reduce the amount of blood in the body and put strain on the heart. 

The CDC also recommends that you seek immediate care if you experience any of the following symptoms with the flu:

  • Persistent pain/pressure in the chest or abdomen
  • Dizziness and confusion 
  • Seizures
  • Not urinating
  • Extreme muscle pain
  • Severe weakness or unsteadiness
  • Cough that improves but then returns or worsens
  • Worsening of chronic medical conditions

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