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H. influenzae

This is the case definition for Haemophilus influenzae serotype a, b, c, d, e, f, undifferentiated and non-typeable.

Case definition

Confirmed case

Clinical evidence of invasive disease with laboratory confirmation of infection: 

  • Isolation of H. influenzae from a normally sterile site, OR
  • Isolation of H. influenzae from the epiglottis in a person with epiglottitis

Probable case

Haemophilus influenzae serotype b

Clinical evidence of invasive disease with laboratory evidence of infection:

  • Demonstration of H. influenzae type b antigen in cerebrospinal fluid, OR
  • Demonstration of H. influenzae DNA in a normally sterile site, OR
  • Buccal cellulitis or epiglottitis in a child less than 5 years of age with no other causative organisms isolated

Definition of clinical illness

Clinical illness associated with invasive disease due to H. influenzae includes meningitis, bacteraemia, epiglottitis, pneumonia, pericarditis, septic arthritis and empyema.


Current vaccination programs only provide coverage for H. influenzae serotype b. However, all H. influenzae isolates that cause invasive disease are considered to meet the case definition for the following three reasons:

  • Most invasive H. influenzae disease is now caused by non-serotype b isolates.
  • Inclusion of all isolates will not change the laboratory diagnosis in any way, as all isolates already require rigorous biochemical tests and serotyping.
  • Data captured on incidence of diseases due to non-type b isolates may have an impact on public health policy and vaccine development in the future.
SOURCE: H. influenzae ( )
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