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When the Flu Turns Deadly

How a nasty virus can be life-threatening and what to do to protect yourself

doctor examines a seriously ill patient in an hospital bed

Fuse/Getty Images

En español | Nanci Ballantyne, 65, is a stickler for getting a flu shot each fall. But the flu season started early this year, the Centers for Disease Control and Prevention confirms, and the development director in Chapel Hill, N.C., got sick before she'd had the chance to roll up her sleeve.

"I was spiking a fever of 102 every day, had a hacking cough that I couldn't shake, chills, fever — all the standard symptoms,” she says. When her symptoms worsened, Ballantyne returned to her physician's office. “I burst into tears and said, ‘I've never been this sick before in my life.’ “

It turned out that Ballantyne's illness had morphed into pneumonia and she needed antibiotics to clear the bacterial infection in her lungs. She was sick for a month, from October 3 until November.

Although Ballantyne was never in serious danger, many people aren't so fortunate. “Depending on the severity of the flu season, about 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,” says Ryan Oyer, M.D., an infectious disease specialist for Kaiser Permanente in Denver.

How sick becomes sicker

Influenza itself can be deadly in vulnerable patients, due to their 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 secretionsas 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.


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"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. “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.

All your risk factors

Age plays a big role in determining who gets sick and how ill they become. People age 60 and older who come down with the flu are more likely to be hospitalized, be put on a breathing machine and die from the illness.

"As you age, your immune system ages, too,” says Joseph Gastaldo, M.D., system head of infectious diseases at OhioHealth, a health care system in central Ohio. “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."

Older people are 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 flu and its repercussions.

The strain of flu virus also influences the seriousness of illness. 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 most devastating influenza pandemic on record, 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. Starting an antiviral medication like oseltamivir (Tamiflu) can reduce the length and severity of illness, if it's taken within the first 48 hours after the onset of symptoms.

Getting vaccinated is still the most important thing you can do to deflect the flu and avoid complications. Each year the vaccine is formulated based on what scientists predict will be the predominant strains of influenza in the coming season. “If the prediction of which strains will circulate does not match well, or the virus itself changes, we may not get optimal protection from the flu vaccine in a given year,” says Oyer. “But generally, there is some protection, even if it is a mismatched vaccine."

And that protection could mean the difference between just feeling wretched for a week and developing pneumonia. Vaccination also lowers a person's chances of having a heart attack or other major cardiac event — or dying from one — over the following year, research shows.

After recovering from the flu, Ballantyne finally got her shot, which may protect her from other flu strains the season may bring. She hopes everybody else will follow her lead. “I wouldn't wish this on anyone,” she says.

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