What are the signs and symptoms of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Initial manifestations of meningitis, seen in more than half of all cases of Haemophilus influenzae type b (Hib) meningitis, include the following:

  • Altered cry

  • Lethargy

  • Nausea or vomiting

  • Fever

  • Headache

  • Photophobia

  • Meningismus

  • Irritability

  • Anorexia

  • Seizures

An altered cry is an important and statistically significant indicator of meningitis or other severe illness, especially in children younger than 2 years; it is noted in as many as 80% of young children with meningitis. Alterations of importance include high-pitched cry, inconsolable crying, weak cry, moaning, or severe reduction or absence of cry. Cry may suggest discomfort or severe distress for which no source outside of the nervous system can be identified.

Lethargy is an early sign in at least half of all cases of bacterial meningitis, versus approximately one third of all viral meningitis cases. Increasing lethargy or the occurrence of convulsive seizures is the usual reason for parents to bring such children to medical attention. These patients should be carefully examined for any evidence of meningismus.

Vomiting is reported as an early manifestation in nearly 50% of Hib meningitis cases. Some data suggest that in individuals with suspected meningitis who have associated vomiting, the lumbar puncture discloses evidence for either bacterial or viral meningitis in 15% of cases. If vomiting occurs, it generally does so within hours to days after the onset of fever.

The presentation of Hib meningitis may be considerably less fulminant than either meningococcal or pneumococcal meningitis, leading to misinterpretation of the initial symptoms or discounting of the significance of the somewhat more leisurely progression of illness. In such subacute cases, fever, irritability, and drowsiness may be the only reported initial signs and symptoms. These subtle manifestations may be mistakenly attributed to a preceding bout of otitis media or other form of upper respiratory illness.

Seizures occur in 23-44% of Hib meningitis cases. They tend to appear during the acute phase, usually within the first 3 days of illness. They are often focal but may secondarily generalize. If this focality is overlooked, seizures due to Hib meningitis may be mistakenly designated as febrile seizures.

Obtaining a history in children younger than 16 months (ie, those at greatest risk for Hib meningitis) may pose particular challenges. The absence of clinical evidence of severe illness cannot be relied upon to exclude the diagnosis of Hib meningitis, particularly in infants and toddlers, whose personal histories cannot readily be obtained. Irritability may be the only presenting sign of Hib meningitis in these young children, and meningismus may be difficult to demonstrate.

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