Lakhasly

Epidemiology H. influenzae is a normal component of the upper respiratory tract flora in humans, and may also colonize the conjunctiva and genital tract.IgA protease produced by the organism degrades secretory IgA, facilitating colo- nization of the upper respiratory tract mucosa.B. Pathogenesis H. influenzae is transmitted by respiratory droplets.

Epidemiology
H. influenzae is a normal component of the upper respiratory tract flora in humans, and may also colonize the conjunctiva and genital tract. Humans are the only natural hosts, and colonization begins shortly after birth, with unencapsulated strains and capsular type b being carried most frequently. H. influenzae illnesses are usually sporadic in occurrence.
B. Pathogenesis
H. influenzae is transmitted by respiratory droplets. IgA protease produced by the organism degrades secretory IgA, facilitating colo- nization of the upper respiratory tract mucosa. From this site, H. influenzae can enter the bloodstream and disseminate to distant sites. Diseases caused by H. influenzae, therefore, fall into two cate- gories (Figure 13.3). First, disorders such as otitis media, sinusitis, epiglottitis, and bronchopneumonia result from contiguous spread of the organism from its site of colonization in the respiratory tract. Second, disorders such as meningitis, septic arthritis, and cellulitis result from invasion of the bloodstream, followed by localization of H. influenzae in these and other areas of the body.