Diseases
| Haemophilus influenzae infection | |
|---|---|
| Classification and external resources | |
| ICD-10 | A49.2 |
| ICD-9 | 041.5 |
| DiseasesDB | 5570 |
| MedlinePlus | 000612 (Meningitis) |
| eMedicine | topic list |
Most strains of H. influenzae are opportunistic pathogens; that is, they usually live in their host without causing disease, but cause problems only when other factors (such as a viral infection, reduced immune function or chronically inflamed tissues, e.g. from allergies) create an opportunity. They infect the host by sticking to the host cell using Trimeric Autotransporter Adhesins (TAA).
Naturally-acquired disease caused by H. influenzae seems to occur in humans only. In infants and young children, H. influenzae type b (Hib) causes bacteremia, pneumonia, and acute bacterial meningitis. On occasion, it causes cellulitis, osteomyelitis, epiglottitis, and infectious arthritis. In fact, Haemophilus influenzae is the most common etiologic agent associated with epiglottitis (thumbprint sign seen on X-Ray).
Due to routine use of the Hib conjugate vaccine in the U.S. since 1990, the incidence of invasive Hib disease has decreased to 1.3/100,000 in children. However, Hib remains a major cause of lower respiratory tract infections in infants and children in developing countries where the vaccine is not widely used. Unencapsulated H. influenzae strains are unaffected by the Hib vaccine and cause ear infections (otitis media), eye infections (conjunctivitis), and sinusitis in children, and are associated with pneumonia.
Read more about this topic: Haemophilus Influenzae
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