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Haemophilus influenzae type b (Hib) can cause serious invasive illness such as meningitis, bacteremia, epiglottitis, and pneumonia. Hib infection is spread primarily by respiratory droplets (droplet spread) produced when an infected person coughs or sneezes. Prior to the introduction of Hib conjugate vaccine in 1987, Hib was the leading cause of bacterial meningitis (causing over 20,000 cases per year) and a major cause of other serious bacterial infections among children under five years of age in the United States. After 1987, Hib cases rapidly declined, and invasive disease from Hib infection is rare today. Non-typeable H. influenzae is rarely responsible for serious illness but is a common cause of ear infections in children. Invasive disease due to Haemophilus influenzae is only reportable in children less than five years of age because this is the age group at risk for severe disease.


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Purpose of surveillance:

  • To facilitate prompt and accurate diagnosis of cases of Haemophilus influenzae serotype b (Hib) disease for investigation
  • To identify contacts of persons with Hib infection and ensure administration of appropriate post-exposure prophylaxis
  • To monitor the occurrence of invasive disease due to non-serotype b H. influenzae

Haemophilus influenzae case data

Local epidemiology:

Two cases of invasive disease caused by Haemophilus influenzae infection in children under five were reported in 2015, both of whom were hospitalized. One case was typed out as serogroup F, and one could not be typed; both cases presented with bacteremia.

Each year in Washington state between four and 11 cases are reported.