Haemophilus influenza is a bacterium that can cause infections, such as pneumonia and ear infections. There are different types of Haemophilus influenza, but the most commonly known type is Haemophilus influenza type b (also called Hib).

More information on Haemophilus influenzae type b


Symptoms generally appear within two to four days. The types of symptoms Hib causes depends on which part of the body is affected by the infection. If the bacterium enters a site in the body where germs normally do not exist, such as spinal fluid or blood (called sterile sites), Hib can cause severe infections that can be debilitating and deadly. This type of infection is called invasive Haemophilus influenzae disease. Some patients who recover from invasive Hib disease (like meningitis) can suffer long lasting neurologic problems, such as deafness.

The most common types of invasive Hib infections are:

  • Bacteremia

  • Meningitis

  • Epiglottitis

  • Cellulitis

  • Infectious arthritis


Haemophilus influenza bacteria are spread through respiratory droplets and through person-to-person contact.

The contagious period varies and, unless treated, can last for as long as the bacteria are present in the nose and throat, even after symptoms have disappeared. A person can no longer spread Hib disease after taking antibiotics for one to two days.

Until recently, Hib was one of the most common cause of bacterial infection in young children. Since an effective vaccine has been available, very few cases of Hib disease are now diagnosed.


Prior to the introduction of the Haemophilus influenza type b vaccine, Hib was the leading cause of bacterial meningitis among children under the age of 5 in the United States.

The American Academy of Pediatrics (AAP) and the Advisory Committee on Immunization Practices (ACIP) recommend that all children be immunized with an approved Hib vaccine series beginning at 2 months of age. For recommendations for scheduling of subsequent doses, consult with your physician. Any licensed Hib conjugate vaccine may be used as a booster dose at age 12–15 months.

More information about the Hib vaccine

Treatment & Prevention

Haemophilus influenzae disease is diagnosed by laboratory tests. Haemophilus influenzae, including Hib disease, is treated with antibiotics, usually for 10 days. 

Sometimes individuals that have been in close or lengthy contact with an infected person may be recommended to take an antibiotic to prevent illness.  This is called prophylaxis. A physician or the Health Department will make recommendations for who should receive prophylaxis.

Last Updated: