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NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

CSTE Position Statement(s)

  • 09-ID-33

Clinical Description

Invasive disease may be manifest as pneumonia, bacteremia, meningitis, epiglottitis, septic arthritis, cellulitis, or purulent pericarditis; less common infections include endocarditis and osteomyelitis.

Case Classification


Meningitis with detection of Haemophilus influenzae type b antigen in cerebrospinal fluid (CSF)


Isolation of Haemophilus influenzae from a normally sterile body site (e.g., blood or CSF, or, less commonly, joint, pleural, or pericardial fluid)


Positive antigen test results from urine or serum samples are unreliable for diagnosis of H. influenzae disease.

The 1997 case definition appearing on this page was originally published in the 1990 MMWR and re-published in the 2009 CSTE position statement 09-ID-33. Thus, the 1990, 1997, and 2010 versions of the case definition are identical.

Related Case Definition(s)