Haemophilus Influenzae

Haemophilus influenzae is a type of bacteria. These bacteria live in the upper respiratory tract. The upper respiratory tract includes the nose, mouth, and throat. 

H. influenzae is often part of the normal bacteria that live in the upper respiratory tract. Sometimes these bacteria can cause infections. Infections can be mild, like ear or sinus infections. They can also be severe, like meningitis and pneumonia.

The Hib Vaccine

 Haemophilus influenzae type b (Hib) is a vaccine-preventable disease. The Hib vaccine protects you, your family and your community.

NC School and Child Care Immunization Requirements

Learn more about requirements for the Hib vaccine.

Invasive Haemophilus influenzae 

An invasive H. influenzae infection is one that affects a "sterile site," which is part of the body that normally does not have any bacteria living in it. 

Examples of sterile sites: 

  • Blood
  • Cerebrospinal fluid
  • Pleural (chest) fluid
  • Synovial (joint) fluid

Examples of non-sterile sites: 

  • Skin
  • Nose
  • Throat
  • Upper respiratory tract

Some bacteria are expected to live in these sites without causing disease. 

Haemophilus influenzae bacteria can cause disease when they get into a sterile site. In North Carolina, invasive H. influenzae infections must be reported to the public health department by health care providers and laboratories. Non-invasive infections do not have to be reported.

Types of Haemophilus influenzae

Specialized laboratory tests can classify Haemophilus influenzae into different types. These types include a, b, c, d, e, f and non-typeable strains. 

Among these, Haemophilus influenzae type b (Hib) is the most dangerous. 

All types of H. influenzae are reported if they cause an invasive infection, even non-typeable strains.

Hib and Meningitis

Meningitis is inflammation (swelling) of the lining of the brain and spinal cord. 

Hib was one of the leading causes of meningitis in children. This was before vaccines becamse widely available. 

Hib meningitis can lead to long-term health problems. These include brain damage, hearing loss, and even death.

Prevention and vaccination

 Since 1990, Hib vaccinations have cut down the number of Hib disease in infants and young children in the U.S.

  • The incidence has decreased by 99%, with fewer than one case per 100,000 children under 5 years of age. 

There are no vaccines for non-type b or non-typeable H. influenzae.

Hib still causes many respiratory tract infections in children where vaccination is not common.

How it spreads

 Hib infections spread through coughing, sneezing or close contact with infected respiratory droplets.

To protect young children, it's important they receive the Hib vaccine.  

Haemophilus influenzae in North Carolina

NCDHHS tracks invasive H. influenzae infections of all types, including non-typeable. In 2024, 302 cases were reported, which is a high point for cases in North Carolina. 

Annual cases have increased since 2012, except for 2020-2022, during the COVID-19 pandemic. 

Over the past five years, 67% of cases in North Carolina were non-typeable. Fewer than 1% were caused by type b. 

Certain age groups are at higher risk for infection. In 2024, the highest rates of cases occurred in people over age 75 and in infants under 12 months. 

Invasive H. influenzae cases are reported throughout the year. Cases are most common in NC during the late autumn and early winter months. 

More information on Haemophilus influenzae trends: 

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This page was last modified on 06/18/2026