Flu Complications

Although most cases of influenza (flu) get better without causing other problems, complications sometimes develop.

Possible problems from the flu include:

• Pneumonia, which is an infection of the lungs. It can be serious in older adults, people who have other health conditions, and in people who are pregnant.
• Bronchiolitis. This is an inflammation of the small airways. It affects infants and can cause a serious lower respiratory infection.
• Sinusitis. This means the mucous membranes that line the inside of the nose and facial sinuses become infected and inflamed.
• Croup. Croup is a swelling or blockage in the windpipe. It causes hoarseness, a barking cough, a high-pitched sound when breathing in, and trouble breathing.
• Worsening symptoms from chronic obstructive pulmonary disease (COPD) or other lung conditions.
• Inflammation of the heart muscle, the sac around the heart, or other muscles in the body.