When the Flu Becomes Dangerous

Find out whom the flu affects the most and learn when—and why—some flu signs may be dangerous.

From painful headaches to body aches to lack of energy, coming down with influenza, aka the flu, is no fun at all. But when it strikes some people, the virus can be more dangerous, even life-threatening. The Centers for Disease Control and Prevention (CDC) reports the 2016-2017 flu season has claimed hundreds of lives already, including over a dozen young children. "Widespread activity" has been reported in 40 of 50 states, and more people are seeing doctors for the illness than in some previous years.

“The flu is a respiratory illness caused by the influenza virus. Symptoms are often mild to severe, but definitely a different illness than a cold,” says emergency medicine specialist Matthew Tincher, MD, of TriStar Horizon Medical Center in Dickson, Tennessee. 

Find out who's at highest risk for an adverse flu reaction and learn when symptoms may warrant emergency care.

People Most at Risk

Because of their weaker immune systems, children under the age of 5—and even more so under age 2—are especially vulnerable to influenza. In fact, the Centers for Disease Control and Prevention (CDC) reports that, each year, over 20,000 children younger than 5 are hospitalized for flu complications. “Children with the flu may show a decreased level of activity, fever, rapid breathing or coughing,” says Dr. Tincher. “Always be aware if they’re not interacting with you as they once were.”

Pregnant Women
Due to changes in their immune system, heart and lungs during pregnancy, pregnant women are at higher risk of severe flu. “Your physiology, blood pressure, blood flow, and heart rate are all different during pregnancy because the baby is taking up a lot of your blood flow and nutrients,” says Tincher.

This sensitivity lasts for up to two weeks after giving birth. The flu can even cause problems with the pregnancy, like premature delivery.

Adults 65 and Older
As people get older, their flu-fighting immune systems become frail. The CDC estimates that between 80 and 90 percent of seasonal flu-related deaths have occurred in seniors over 65. “Their immune systems are not fully active, so it’s easier for them to pick up the virus,” says Tincher.

Those with Medical Conditions
The flu weakens your body and can exacerbate an already existing health problem, which is why people with certain conditions may have a harder time coping with the virus. Plus, these conditions make people more susceptible to flu complications like pneumonia, and having the flu can make these other health problems worse. The best example is diabetes. Infections like the flu make it harder to control blood sugar. Conditions that may worsen from the virus include:

  • Asthma
  • Diabetes
  • Neurological conditions
  • Chronic lung disease (i.e., COPD and cystic fibrosis)
  • Heart disease
  • Liver and kidney disorders
  • Blood disorders (i.e., sickle cell disease)
  • Weakened immune systems due to disease or medications (i.e., cancers or HIV and AIDS)
  • Severe obesity

If you begin to experience flu-like symptoms and have any of these medical conditions, talk to your doctor so you can take the proper precautions.

When Emergency Care May Be Necessary
A normal case of the flu usually comes on suddenly and lasts anywhere from one to two weeks. People may have a fever or the chills, cough, runny or stuffy nose, sore throat, headaches, fatigue and muscle aches.

For those who may be more susceptible to the virus, however, more serious complications may occur, such as pneumonia, sinus or ear infections, bronchitis and seizures.

“It’s important to say that not everybody with the flu needs to come to the emergency department,” says Tincher. “The vast majority of healthy adults and children can get treatment for the flu in their doctor’s office if they’re only mildly ill.”

Contact your doctor immediately if you or a loved one experience any of these warning signs during a bout with the flu:

  • Difficulty breathing or shortness of breath
  • Severe or persistent vomiting
  • Chest or belly pain
  • Sudden dizziness
  • Confusion
  • Symptoms that get better, then return with fever and worse cough
  • Severe dehydration

In infants and children, watch for: trouble breathing, a high fever with a rash, no urination or lack of tears when crying, or skin that is bluish in color. “A healthy child should be active, smiling, and playful,” says Tincher. “If they’re not those things, then they need to be seen in an emergency department.”

Your Best Bet at Prevention
The CDC recommends everyone six months and older receive a flu vaccination each year. Research shows that vaccination typically reduces flu risk by about 50 to 60 percent. It also makes the illness less severe, and protects against dangerous complications. And don't think it's ever too late—or too early—for a vaccine. While outbreaks peak between December and February, flu cases can occur as late as May and as early as October. 

For kids, it’s best to get the flu shot rather than the nasal spray, which is falling out of favor, says Tincher: “The CDC has stopped recommending that we give our children the FluMist.” There’s also a high-dose vaccine available for those 65 and older. In one trial of 30,000 people, seniors who had the high-dose shot had a 24 percent lower chance of catching the flu.

In addition to the flu shot, Tincher also recommends staying away from people who are sick, staying home at least 24 hours if you have a fever and covering your mouth when you cough. 

This content was updated on February 6, 2017.