What are possible complications of the flu?

Dr. Jeanne Morrison, PhD
Family Practitioner

One common complication of influenza (flu) is pneumococcal pneumonia, a lung infection caused by bacteria. This can be a serious, even life-threatening, infection, especially for the elderly, people with weak immune systems, or people with chronic diseases. In addition, some people may get ear infections, sinusitis, or bronchitis as a result of influenza. Those with asthma, diabetes or congestive heart failure may find that their condition is aggravated by influenza.

Stacy Wiegman, PharmD
Pharmacy Specialist

Some common complications of influenza (the flu) include the following conditions:

  • pneumonia
  • ear infections
  • sinus infections
  • bronchitis

What's more, contracting the flu can worsen chronic medical conditions, such as asthma or heart disease. Children, pregnant women and older men and women are more likely than others to have complications from the flu. Also, American Indians and Alaskan Natives may have a high risk for flu-related complications, according to the U.S. Centers for Disease Control and Prevention (CDC). 

The CDC recommends that certain at-risk children and older adults and those with chronic diseases get a pneumonia vaccination. Check with your healthcare provider about whether you should also receive a pneumonia vaccination.

Most people who get the flu get better in several days to less than two weeks. However, some people develop flu-related complications. The flu, or influenza, can cause many complications of the upper respiratory tract (nasal passages, throat) and lower respiratory tract (lungs). While anyone can get sick with the flu and become severely ill, some people are more likely to experience severe flu illness. Young children, adults aged 65 years and older, pregnant women, and people with certain chronic medical conditions are among those at high risk of serious flu complications, which can lead to a hospital stay and, sometimes, even death. For example, people with chronic lung disease are at higher risk of developing severe pneumonia.

Flu also can make chronic medical problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic heart disease may experience a worsening of this condition triggered by the flu.
Moderate complications from the flu include:

  • sinus infection
  • ear infection

Serious complications from the flu include:

  • pneumonia
  • inflammation of the heart (myocarditis)
  • inflammation of the brain (encephalitis)
  • inflammation of the muscle or tissues (myositis, rhabdomyolysis) tissues
  • multi-organ failure (for example, respiratory and kidney failure) 

Flu virus infection of the respiratory tract also can trigger an extreme inflammatory response in the body that can lead to sepsis, the body’s life-threatening response to infection.

The most serious, often life-threatening complication of the flu is pneumonia. Other complications include ear infection, bronchitis, dehydration and worsening of chronic conditions such as congestive heart failure, asthma or diabetes. Croup and a lung disease called bronchiolitis can also arise as complications in infants and young children.

There is also evidence that influenza can be more dangerous for women in their second or third trimester of pregnancy. The strain and stress of pregnancy on a woman's lungs, combined with the type of influenza, can lead to pulmonary problems.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.