[Epidemiologic aspects of Haemophilus influenzae type b infection]

This paper reviews the role of Haemophilus influenzae type b (Hib) as one of the most important pathogens causing invasive infectious diseases, especially in the first 2 years of life. In developing countries H. influenzae is responsible for 30% of all pneumonia cases with positive cultures and for 20% to 60% of all bacterial meningitis cases. In this study we compared Brazilian and international epidemiologic data obtained from several bibliographic databases (MEDLINE, 1966 to 1995; LILACS, 1982 to 1995; Thesis Databank, 1980 to 1995; and Dissertation Abstracts, 1988 to 1994). The incidence of Hib infection in Brazil was analyzed for individual states and for different ages, including within the first year of life. Meningitis cases were used as an incidence marker because of the difficulty in identifying the causative organism in such other infections as pneumonia, osteomyelitis, epiglottitis, cellulitis, and endocarditis. Our analysis showed that the nationwide Brazilian data masked the regional incidence and lethality of H. influenzae. For example, in 1991 the national incidence was 18.4 per 100,000 children under 1 year of age. In the same period, the Federal District had an incidence of 175 per 100,000 among children between 4 and 6 months of age. Similarly, the North of Brazil had a 35% case fatality rate in 1987, whereas the rate was 22% for Brazil as a whole. This study raises issues concerning the relevant epidemiologic factors associated with Hib infection and the costs and benefits of prophylaxis and vaccination in the age groups most at risk.