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Haemophilus influenzae
Last reviewed: 04.07.2025
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Haemophilus influenzae infection is an acute anthroponotic infectious disease with an aerosol mechanism of transmission of the pathogen, which is characterized by predominant damage to the respiratory tract and meninges.
Haemophilus sp causes a wide variety of mild to severe infections, including bacteremia, meningitis, otitis media, cellulitis, and epiglottitis. Diagnosis of Haemophilus influenzae infection is based on culture and serotyping. Treatment of Haemophilus influenzae infection is with antibiotics.
ICD-10 codes
- A41.3. Septicemia caused by Haemophilus influenzae (Afanasyev-Pfeiffer bacillus).
- A49.3. Infection caused by Haemophilus influenzae, unspecified.
- B96.3. Haemophilus influenzae as the cause of disease classified elsewhere.
- J14. Pneumonia due to Haemophilus influenzae.
What causes Haemophilus influenzae infection?
Haemophilus influenzae is caused by several pathogenic Haemophilus species, the most common of which is Haemophilus influenzae. There are 6 encapsulated strains (a–f) and countless nonencapsulated, nontypeable strains. Before the use of the Haemophilus influenzae type b (Hib) conjugate vaccine, most cases of serious invasive disease were due to Haemophilus influenzae type b, which causes many childhood infections including meningitis, bacteremia, septic arthritis, pneumonia, tracheobronchitis, otitis media, conjunctivitis, sinusitis, and acute epiglottitis. These infections, as well as endocarditis, may also occur in adults, although much less frequently. These diseases are discussed in the relevant articles. Nonencapsulated strains occasionally cause invasive disease.
What are the symptoms of Haemophilus influenzae infection?
Haemophilus influenzae, serotype aeruginosa, can cause mucopurulent conjunctivitis and bacteremic Brazilian purple fever. Haemophilus ducreyi causes chancroid. Haemophilus parainfluenzae and Haemophilus aphrophilus are rare causes of bacteremia, endocarditis, and brain abscess.
Many Haemophilus are normal flora of the upper respiratory tract and rarely cause disease. Pathogenic strains enter the upper respiratory tract through airborne aerosols or direct contact. Spread of infection occurs rapidly in nonimmune populations. Children are at high risk for developing serious infections, especially black boys and Native Americans. Living in crowded places and attending day care predispose to infection. Immunodeficiency states, asplenia, and sickle cell anemia also predispose to infection.
How is Haemophilus influenzae diagnosed?
Diagnosis of hemophilic infection is based on a cultural study of blood and biological fluids. Strains responsible for invasive disease are subject to serotyping.
What do need to examine?
How is Haemophilus influenzae infection treated?
Treatment of Haemophilus influenzae infection depends on the nature and location of the infection, but invasive forms of infection include doxycycline, fluoroquinolones, second- and third-generation cephalosporins, and carbapenems. The use of Hib vaccine has significantly reduced the incidence of bacteremia. Children with severe forms of infection should be hospitalized with respiratory and contact isolation for 24 hours after initiation of antibacterial therapy. The choice of antibiotic depends on the site of infection and requires determination of the susceptibility of the organism to antibacterial drugs. Many isolates of this organism in the United States produce beta-lactamase. Cefotaxime and ceftriaxone are recommended for invasive infection, including meningitis. Oral cephalosporins, macrolides, and amoxicillin-clavulanate are usually effective for less severe forms of infection.
How is Haemophilus influenzae infection prevented?
Hib conjugate vaccine against Haemophilus influenzae can be used in children over 2 months of age. This vaccine reduces the incidence of invasive infections such as meningitis, bacteremia and epiglottitis by 99%. Primary series of vaccinations are given at 2, 4 and 6 months or at 2 and 4 months, depending on the vaccine manufacturer. A booster dose is given at 12-15 months of age.
Household contacts may result in asymptomatic carriage of Haemophilus influenzae. Unimmunized or incompletely immunized contacts under 4 years of age are at high risk of developing the disease and should receive a dose of vaccine. In addition, all household members (excluding pregnant women) should receive prophylactic medication with rifampin 600 mg (20 mg/kg for children) orally once daily for 4 days. Contacts of service personnel or contacts within a daycare facility should receive prophylactic medication if 2 or more cases of invasive infection occur within 60 days. There is no evidence that prophylactic medication is needed after 1 case of infection.