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The following text is from an archived Red Book® edition and may not reflect current recommendations or information. To view the current edition, click here.
Section 3. Summaries of Infectious Diseases
Haemophilus influenzae Infections
Clinical Manifestations
Etiology
Epidemiology
Diagnostic Tests
Treatment
Isolation of the Hospitalized Patient
Control Measures (for invasive Hib disease)
CLINICAL MANIFESTATIONS: Haemophilus influenzae causes conjunctivitis, otitis media, sinusitis, epiglottitis, pneumonia, empyema, septic arthritis, cellulitis, meningitis, and occult febrile bacteremia. Other H influenzae infections include purulent pericarditis, endocarditis, endophthalmitis, osteomyelitis, peritonitis, glossitis, uvulitis, and septic thrombophlebitis. Occasionally, other encapsulated and nonencapsulated strains cause septicemia, otitis media, sinusitis, bronchitis, pneumonia, and meningitis, including infection in neonates.
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ETIOLOGY: Haemophilus influenzae is a pleomorphic gram-negative coccobacillus. Encapsulated strains express 1 of 6 antigenically distinct capsular polysaccharides (a through f); nonencapsulated strains fail to react with typing antisera against capsular serotypes a through f and are designated nontypeable.
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EPIDEMIOLOGY: The natural habitat of the organism is the human upper respiratory tract. The mode of transmission is person-to-person by inhalation of respiratory droplets or by direct contact with respiratory secretions. In neonates, infection is acquired intrapartum by aspiration of amniotic fluid or by contact with genital tract secretions containing the organism. Asymptomatic colonization by H influenzae strains is common; nonencapsulated strains are recovered from the nasopharynx of 40% to 80% of children. Colonization by type b organisms is rare, occurring in 2% to 5% of children in the prevaccine era and even fewer individuals currently, because immunization decreases pharyngeal colonization. The exact period of communicability is unknown.
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Before introduction of effective H influenzae type b (Hib) conjugate vaccines, Hib was the most common cause of bacterial meningitis in children in the United States. The peak incidence of meningitis and most other invasive Hib infections occurred between 6 and 18 months of age, accounting for approximately 45% of cases in children younger than 5 years of age. In contrast, the peak for
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