Although most cases of
influenza (flu) get better without causing other
problems, complications sometimes develop.
of flu include:
Pneumonia, which is an inflammation of
- Primary influenza viral pneumonia develops
soon (24 to 36 hours) after flu symptoms start and does not get better with
antibiotics. It rarely causes death in young, healthy people, but it can often
be life-threatening in older adults, people who have other diseases, and
- Secondary bacterial pneumonia most often develops
after a period of improvement following the flu. People with this type of
pneumonia usually get better with antibiotics.
- Bronchiolitis, which is an inflammation
of the small air passages (bronchioles). Bronchiolitis affects infants and is the leading cause of serious lower
which is an infection or inflammation of the mucous membranes that line the
inside of the nose and facial sinuses. Facial sinuses are hollow spaces, or
cavities, located around the eyes, cheeks, and nose.
- Croup, which is a swelling or obstruction in the
windpipe (trachea). It causes a distinctive hoarseness and a barking cough, a
high-pitched sound (stridor) heard when breathing in, and trouble
- Chronic obstructive pulmonary disease (COPD) getting worse.
- Reye syndrome, which is a very rare but
serious disease that most often occurs in children 6 to 12 years old. The exact
cause is not known. But it is associated with children who have recently had
chickenpox (varicella) or flu (influenza) and have taken aspirin. The disease
primarily targets the brain and liver and can cause drowsiness, confusion,
seizures, coma, and in severe cases, death.
- Inflammation of the
heart muscle (myocarditis), inflammation of muscles (myositis), or inflammation
of the sac around the heart (pericarditis).
- Fatigue and a lack of
energy that persist after flu symptoms are gone. People may take several weeks
to fully recover, although no cause for the symptoms has been