Haemophilus influenzae b disease, invasive

Reporting Obligations

Suspected cases must be reported immediately by phone to the Thunder Bay District Health Unit at 625-8318 or toll-free 1-888-294-6630, ext. 8318 (Monday-Friday, 8:30am to 4:30pm). After hours and on weekends/holidays call Thunder Bay Answering Service at (807) 624-1280.


Aetiologic Agent:

Haemophilus influenzae serotype b (Hib) is a gramnegative encapsulated coccobacilli bacterium that causes invasive disease and illness. H. influenzae strains 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. Only type b strains are reportable.

Clinical Presentation:

Meningitis is the most common clinical manifestation of invasive Hib disease, followed by epiglottitis and bacteremia. 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. Epiglottitis is a medical emergency as swelling of the epiglottis can lead to airway obstruction which can be life-threatening. Other manifestations of invasive disease include pneumonia, septic arthritis, cellulitis, otitis media, and purulent pericarditis.

Modes of transmission:

Transmission is person-to-person most commonly through the nasopharynx by inhalation of respiratory droplets or by direct contact with nasal or throat secretions from an infected person during the infectious period.

Incubation Period:

Unknown but probably short, 2-4 days.

Period of Communicability:

As long as Hib bacteria are present, which may be for a prolonged period of time even without nasal discharge. Communicability ends within 24 to 48 hours after starting effective antibiotic therapy.


Risk Factors/Susceptibility

Susceptibility is universal. Risk factors include being immunocompromised, unimmunized, or incompletely immunized.


Diagnosis & Laboratory Testing

Call your local Public Health Laboratory prior to collection. Laboratory testing for Hib infection includes, standard culture with serotyping, antigen test, and nucleic acid amplification test (NAT). Samples are from sterile sites (e.g. cerebrospinal fluid, blood) or from epiglottis in a person with epiglottitis.

Testing Information & Requisition


Treatment & Case Management

Invasive Hib disease often requires hospitalization and immediate initiation of antimicrobial therapy to eliminate Hib colonization. Cases who are less than two years of age or who are a member of a household with a susceptible contact should additionally receive rifampin chemoprophylaxis prior to hospital discharge if cefotaxime or ceftriaxone were not used for treatment.

Provide the family with information about the illness and immunization. Inform them that a child who has recovered from invasive Hib disease should receive Hib conjugate vaccine because natural infection may not provide adequate protective antibodies.

Close contacts of a Hib case will be identified and followed by Public Health staff to determine eligibility for chemoprophylaxis. Chemoprophylaxis is recommended to eliminate nasopharyngeal carriage of Hib bacteria and prevent secondary transmission. To effectively prevent secondary spread, rifampin chemoprophylaxis is recommended for household and child care contacts in specific situations. If chemoprophylaxis is indicated, rifampin dosages should be administered as soon as possible.


Patient Information

Patient Fact Sheet



  1. Ministry of Health and Long Term Care, Infectious Diseases Protocol, 2018.  Appendix A (2018) and Appendix B (2018)


Additional Resources

  1. MOHLTC. “Publicly Funded Immunization Schedule for Ontario”, December 2016.
  2. Public Health Agency of Canada. “Haemophilus influenzae disease.”
Last Updated: 07/05/2019