Background: The incidence by age and causative organism of bacterial meningitis are not known on a community basis.
Methods: The epidemiology of bacterial meningitis in a metropolitan county was studied by identifying all cases admitted to a hospital from 1983 through 1987.
Results: The overall incidence of bacterial meningitis was 5 per 100,000 person-years, but numbers of cases ranged from 40 per 100,000 for children younger than 5 years to 1.0 per 100,000 in adults aged between 16 and 64 years. No significant excesses of cases were found in male patients or in blacks. The predominant causative organism varied with age. Overall, Haemophilus influenzae was the most common causative organism, but 32 percent of cases were due to Streptococcus pneumoniae. Case fatality rates were high for S. pneumoniae (12.5 percent) and very high for the small number of elderly patients suffering from bacterial meningitis.
Conclusions: Significant declines have occurred in the last decade in the incidence of bacterial meningitis in children, particularly in those younger than 5 years, and in disease caused by H. influenzae and group B streptococcus.