How does the incidence of Haemophilus influenzae type b (Hib) meningitis vary by season?

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

In the temperate countries in the Northern Hemisphere, including the United States, the seasonal incidence of Hib meningitis follows a bimodal distribution, with the first peak in June and the second in September to October.

This seasonal pattern differs significantly from that of the other 2 major causes of human meningitis, N meningitidis and S pneumoniae, both of which occur most frequently in the winter months. It differs from that of conditions such as sporadic herpes encephalitis or epidemic conditions such as mumps encephalitis, which occur year-round, although this difference is of little help in determining the differential diagnosis.


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