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In 1986, the Centers for Disease Control (CDC) in Atlanta, Georgia, along with six different state and local health departments, conducted a survey of all reported cases of meningitis. Meningitis is an inflammation of the meninges, membranes surrounding the brain and spinal cord. The five most common causes of bacterial meningitis are S. pneumoniae, H. influenzae, Listeria monocytogenes, Neisseria meningitidis and group B streptococcus. The survey monitored the occurrence of these different types of meningitis in 34 million people. The most common bacterial cause of meningitis was H. influenzae, occurring in 45 percent of the study group. Streptococcus pneumoniae was identified in 18 percent of the population and Neisseria meningitidis in 14 percent. The most common cause of bacterial meningitis in children less than one month of age and in the elderly over 60 years of age was group B streptococcus. The overall fatality rate was lowest for H. influenzae (3 percent) and highest for L. monocytogenes (22 percent). These fatality rates are significantly lower than those reported in a study in the early 1970s. However, 32 percent of the H. influenzae isolates were resistant to ampicillin, compared with 24 percent reported in 1981. (Consumer Summary produced by Reliance Medical Information, Inc.)