How is seasonal variation used to differentiate Haemophilus influenzae type b (Hib) meningitis from other forms of 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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Seasonal variation in incidence of Hib meningitis

Time of year is an important factor in differentiating Haemophilus influenzae type b (Hib) meningitis from cases due to the other 2 major causes of human meningitis, N meningitidis and Streptococcus pneumoniae. Hib meningitis has a bimodal distribution, with the first peak in June and the second in September to October. In contrast, the incidence of meningococcal and pneumococcal meningitis is greatest in the winter months.

The increased Hib prevalence in summertime corresponds somewhat, but not exactly, to the period of highest prevalence of arboviral encephalitis, aseptic meningitis, enteric encephalitides such as poliomyelitis or coxsackie encephalitis, and tick-borne encephalitides such as Lyme disease or Rocky Mountain spotted fever. Many of these differential considerations have their highest prevalence in July to August.

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