Haemophilus influenzae

Haemophilus influenzae


Haemophilus influenzae is a common cause of respiratory tract infections. Most strains of H. influenzae are opportunistic pathogens, i.e. they live in their host without causing invasive disease unless other factors such as viral infections or compromised immunity create the opportunity.

H. influenza can be encapsulated or non-encapsulated. The non-encapsulated or non-typable strains are very common in the airways, and often cause respiratory infections including bronchitis, ear infections and, sometimes, invasive disease like bloodstream infections in susceptible hosts.

H. influenza type b (Hib) is a rare serotype that is particularly dangerous to infants and young children who, if unvaccinated, are susceptible to severe invasive infection. Hib disease can manifest as meningitis, epiglottitis, pneumonia, arthritis, and cellulitis. The polysaccharide capsule of Hib is primarily responsible for its virulence.


Only Hib is preventable through vaccination. Until the introduction and routine use of the Hib vaccine, H. influenzae type b was the leading cause of bacterial meningitis in infants and children in this country. With the introduction and routine use of Hib conjugate vaccines since ~1990, Hib disease has now become rare. The vaccine decreases the rate of carriage of Hib among vaccinated children, thereby decreasing the chance that unvaccinated persons will be exposed. While Hib disease has nearly disappeared in the United States and the developed world, the cost of the conjugate vaccine has limited its use in developing countries where the disease remains a major cause of morbidity and mortality.

For a detailed schedule of Hib vaccination recommendations, refer to recommendations published by the Advisory Committee on Immunization Practices (ACIP) or consult the Georgia Immunization Program.

Under specific circumstances, prophylaxis may be recommended for persons exposed to invasive Hib disease. These circumstances include prophylaxis of family members if an unprotected or under-protected child is in the home, and daycare contacts if 2 or more Hib cases occur in that setting. For more information on Hib prophylaxis, see the American Academy of Pediatrics, Committee on Infectious Diseases "Redbook."

All hospitals and labs are encouraged to promptly submit* isolates of Haemophilus influenzae to:

Georgia Public Health Laboratory 
Bacteriology Unit 
1749 Clairmont Road 
Decatur, GA 30033

The following form is to be used when submitting isolates:  Bacteriology Submission Form

  • In the Atlanta Metro Statistical Area (MSA), isolates are picked up by EIP personnel.

More about Haemophilus influenzae:

Updated 12/27/2022