Haemophilus influenzae meningitis

Jeffrey A Rumbaugh MD (Dr. Rumbaugh of the Johns Hopkins University has no relevant financial relationships to disclose.)
Karen L Roos MD FAAN, editor. (

Dr. Roos of Indiana University School of Medicine has no relevant financial relationships to disclose.

Originally released February 28, 2005; last updated September 8, 2009; expires September 8, 2012
Notice: This article has expired and is therefore not available for CME credit.

This article includes discussion of Haemophilus influenzae meningitis, Haemophilus influenzae, Haemophilus influenzae type b, Hib, H influenzae, and H flu. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Meningitis is the most serious form of Haemophilus influenzae infection, historically causing significant mortality and morbidity, especially among children. Vaccination against H influenzae type b has dramatically decreased the impact of this disease, making recognition more difficult when it occurs. In this article, the author reviews the clinical manifestations and pathophysiology of H influenzae infection, with emphasis on the key features useful for making a timely diagnosis. Recent research has elucidated the factors involved in the inflammatory response to this organism, and new PCR-based techniques for confirming the diagnosis have been developed. The most recent vaccination guidelines and current treatment recommendations are discussed.

Historical note and terminology

Haemophilus influenzae was first isolated by Pfeiffer during the 1889 influenza pandemic (Pfeiffer 1893), and it was believed to be the causative agent of influenza. It was called the “influenza bacillus.” Eventually, the error of this diagnostic association was recognized. The organism was given the genus name Haemophilus, meaning “blood-loving,” and the species name influenzae in recognition of the historical association.

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