Which clinical history findings suggest 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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Answer

Some elements of the history are helpful in establishing the possibility that a patient with possible meningitis has Hib meningitis. These risk factors are pertinent to children older than 2 months and younger than 5 years.

Time of year is a factor. Presentation between June and November is suggestive of Hib meningitis (in the temperate or sub-Arctic latitudes of the Northern hemisphere).

Vaccination status—both group and individual—is important. With a child who is a member of an unvaccinated population, the likelihood of meningitis being caused by Hib is as high as 95%. A child presenting with meningitis who has not been vaccinated against Hib has a considerably greater chance for Hib diagnosis. Hib remains the most common cause of meningitis in unvaccinated children aged 2 months to 5 years even in a vaccinated population.

Although Hib vaccines have considerably reduced the likelihood that Hib is the cause of meningitis in children in this age group, they have not eliminated Hib meningitis in this naturally susceptible population, especially those children with compromised immune function. Remember that Hib-immunized children may develop Haemophilus meningitis because of unrecognized immunodeficiency or vaccine failure or because they are infected with an untypable or non-B Haemophilus strain.

A history of a presumed viral upper respiratory illness or otitis media preceding the onset with an intervening period of improvement or recovery is fairly characteristic of Hib meningitis. From 60-80% of children who develop Hib meningitis have had otitis media or an upper respiratory illness (presumably viral) immediately before the onset of meningitis; others develop Hib meningitis after a presumably viral gastrointestinal (GI) illness. A meningitic presentation in the wake of epiglottitis may be particularly suggestive of Hib etiology, although this presentation is uncommon.


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