Types of Haemophilus influenzae Infections

H. influenzae most often cause pneumonia, but can also cause severe illnesses like meningitis and bloodstream infections.

Haemophilus influenzae, a type of bacteria, can cause many different kinds of infections. These infections range from mild, ear infections, to serious, like bloodstream infections.

Doctors consider some of these infections “invasive.” Invasive disease happens when the bacteria invade parts of the body that are normally free from germs. For example, H. influenzae can invade the spinal fluid, causing meningitis, or bloodstream, causing bacteremia. Invasive disease is usually serious, requiring treatment in a hospital, and can sometimes result in death.

The most common types of invasive disease caused by H. influenzae are:

  • Pneumonia* (lung infection)
  • Bloodstream infection
  • Meningitis
  • Epiglotittis (swelling in the throat)
  • Cellulitis (skin infection)
  • Infectious arthritis (inflammation of the joint)

H. influenzae can also be a common cause of ear infections in children and bronchitis in adults. Learn more about these illnesses.


*Doctors consider pneumonia an invasive infection when H. influenzae also infects the blood or fluid surrounding the lungs.

Page last reviewed: February 13, 2020