Haemophilus influenzae

Haemophilus influenzae causes diseases predominantly affecting children.

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

Laboratory Testing

  • CDC – testing recommendations
  • Rapid antigen detection tests are available – utility is questionable
  • Otitis/sinusitis – clinical diagnosis; laboratory testing not routinely performed
  • Pneumonia – CBC, chest x-ray; consider sputum culture, blood culture
    • Positive upper respiratory culture does not necessarily establish organism as pathogen due to colonization
  • Cellulitis – wound culture; consider CBC, depending on clinical severity
  • Meningitis – CBC, spinal tap with cerebrospinal fluid (CSF) culture and gram stain, cell count
  • Immunoglobin deficiency testing
    • IgG testing for diphtheriatetanus, and H. influenzae – determine vaccination response to diagnose immunoglobulin deficiency in patients with recurrent infection
      • Need pre- and postvaccine titers (1 month after vaccination)

Differential Diagnosis


  • Incidence
    • WHO – 3,000,000 cases of serious disease annually
    • <1/100,000 for invasive disease in U.S. for children <5 years (CDC, National Notifiable Disease Surveillance System [NNDSS], 2015)
  • Age – usually in children; exception is pneumonia, which affects all ages
  • Transmission – respiratory droplet or direct contact with secretions

Risk Factors


  • Small, gram-negative bacterium
    • Nonmotile
    • Nonspore forming
    • Fastidious
  • Requires medium containing X (porphyrins such as hemin) and V (nicotinamides such as nicotinamide adenine dinucleotide [NAD]) factors for aerobic growth (eg, chocolate agar)
  • Six major typeable serotypes (A-F)
    • Nontypeable strains are common and felt to be disease causing
  • Colonizes human upper airways
    • Up to 80% of healthy people carry nontypeable H. influenzae

Clinical Presentation

  • Invasive disease significantly decreased since vaccine introduced
  • Otitis media, sinusitis, pharyngitis – usually children
  • Cellulitis – predominantly young children
  • Pneumonia – elderly, patients with chronic obstructive pulmonary disease (COPD), and patients who are immunocompromised
    • Common etiology of COPD exacerbations
  • Meningitis – often preceded by symptoms of upper respiratory tract infection, head trauma or surgery, cerebrospinal fluid (CSF) leak, otitis or sinusitis
  • Epiglottitis – usually children
  • Bacteremia (sepsis) – neonatal and maternal sepsis
  • Septic arthritis – usually children <2 years
  • Conjunctivitis – may occur in outbreaks, especially in daycare settings
Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Diphtheria, Tetanus, and H. Influenzae b Antibodies, IgG 0050779
Method: Quantitative Multiplex Bead Assay

CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Cell Count, CSF 0095018
Method: Cell Count/Differential

Respiratory Culture and Gram Stain 0060122
Method: Stain/Culture/Identification

Blood Culture 0060102
Method: Continuous Monitoring Blood Culture/Identification


Testing is limited to the University of Utah Health Sciences Center only

Low volume will result in decreased recovery of pathogens

Cerebrospinal Fluid (CSF) Culture and Gram Stain 0060106
Method: Stain/Culture/Identification

Explify Respiratory Pathogens by Next Generation Sequencing 2013694
Method: Massively Parallel Sequencing


U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Manual for the Surveillance of Vaccine-Preventable Diseases. Centers for Disease Control and Prevention. Atlanta, GA [Last updated Apr 2016; Accessed: Aug 2017]

U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Recommended Immunization Schedules for Children and Adolescents Aged 18 Years or Younger. United States, 2016. Centers for Disease Control and Prevention. Atlanta, GA [Last Updated Jan 2017; Accessed: Sep 2017]

General References

Rudan I, Campbell H. The deadly toll of S pneumoniae and H influenzae type b. Lancet. 2009; 374(9693): 854-6. PubMed

Ulanova M, Tsang RS. Invasive Haemophilus influenzae disease: changing epidemiology and host-parasite interactions in the 21st century. Infect Genet Evol. 2009; 9(4): 594-605. PubMed

Watt JP, Wolfson LJ, O'Brien KL, Henkle E, Deloria-Knoll M, McCall N, Lee E, Levine OS, Hajjeh R, Mulholland K, Cherian T, Hib and Pneumococcal Global Burden of Disease Study Team. Burden of disease caused by Haemophilus influenzae type b in children younger than 5 years: global estimates. Lancet. 2009; 374(9693): 903-11. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

Medical Reviewers

Last Update: October 2017