Epidemiology of Haemophilus influenzae type b infections

Haemophilus influenzae type b is a human bacterial pathogen that causes approximately 12,000 cases of H influenzae type b meningitis and 7500 cases of other forms of invasive disease annually in the United States. This organism is the leading cause of bacterial meningitis in the United States. The cause of meningitis can be established more accurately than that of other forms of invasive bacterial disease because the isolation of the bacterium from the cerebrospinal fluid or blood and/or the detection of bacterial antigen can correctly attribute the infection to a specific bacterial agent and dictate appropriate antimicrobial therapy. In children, more than 95% of all invasive diseases attributable to Haemophilus species, including septicemia, pneumonia, epiglottis, cellulitis, arthritis, osteomyelitis, and pericarditis, are due to H influenzae type b. It has been estimated that systemic disease caused by H influenzae type b occurs in approximately 1 in 200 children in the United States before the age of five. The case fatality rate for H influenzae type b meningitis is approximately 5%, and substantial morbidity has also been documented to result from central nervous system infection with this agent. Of surviving children reported in a 1969 paper, 40% had significant neurologic sequelae after meningitis. A more recent study demonstrated substantial neurologic improvement during the first few months after hospitalization, but at 1 year of age 8% of the children had neurologic or intellectual sequelae of their meningitis. Milder defects with an array of developmental problems have been reported in as many as one third to one half of all survivors.(ABSTRACT TRUNCATED AT 250 WORDS)