Appendix A: Disease-Specific Chapters Chapter: Haemophilus influenzae type b disease, invasive Revised January 2014
Haemophilus influenzae type b disease, invasive Communicable Virulent Health Protection and Promotion Act: Ontario Regulation 558/91 – Specification of Communicable Diseases Health Protection and Promotion Act: Ontario Regulation 559/91 – Specification of Reportable Diseases
1.0 Aetiologic Agent Haemophilus influenzae serotype b (Hib) is a gram-negative encapsulated coccobacilli bacterium that causes invasive disease and illness. H. influenzae strains are either encapsulated (typeable) or non-encapsulated (nontypeable). Encapsulated strains (classified a-f) are more likely to cause invasive disease than non-encapsulated strains, which cause mild infection.1 Only type b strains are reportable.
2.0 Case Definition 2.1 Surveillance Case Definition See Appendix B.
2.2 Outbreak Case Definition Not Applicable.
3.0 Identification 3.1 Clinical Presentation Meningitis is the most common clinical manifestation of invasive Hib disease, followed by epiglottitis and bacteremia.1 Onset of symptoms can be subacute, but is usually sudden, including fever, vomiting, lethargy and meningeal irritation with bulging fontanelle in infants or stiff neck and back in older children.1 Epiglottitis is a medical emergency as swelling of the epiglottis can lead to airway obstruction which can be life-threatening.2, 3 Other manifestations of invasive disease include pneumonia, septic arthritis, cellulitis, otitis media, and purulent pericarditis.2
3.2 Diagnosis See Appendix B for diagnostic criteria relevant to the Case Definitions. For further information about human diagnostic testing, contact the Public Health Ontario Laboratories or refer to the Public Health Ontario Laboratory Services webpage: http://www.publichealthontario.ca/en/ServicesAndTools/LaboratoryServices/Pages/default.as px 2
4.0 Epidemiology 4.1 Occurrence Between 2007 and 2011, an average of four cases of Hib occurred per year in Ontario. For more information on infectious diseases activity in Ontario, refer to the current versions of the Ontario Annual Infectious Diseases Epidemiology Reports and the Monthly Infectious Diseases Surveillance Report.4, 5 Hib was the most common cause of bacterial meningitis and a leading cause of other serious invasive infections in young children before the introduction of Hib vaccines in 1998.6 Incidence of Hib remains highest in infants
