A prospective, laboratory-based surveillance project obtained accurate data on meningitis in a population of 34 million people during 1986. Haemophilus influenzae was the most common cause of bacterial meningitis (45%), followed by Streptococcus pneumoniae (18%), and Neisseria meningitidis (14%). Rates of H. influenzae meningitis varied significantly by region, from 1.9/100,000 in New Jersey to 4.0/100,000 in Washington state. The overall case fatality rates for meningitis were lower than those reported in several studies from the early 1970s, suggesting that improvements in early detection and antibiotic treatment may have occurred since that time. Concurrent surveillance was also performed for all invasive disease due to the five most common causes of bacterial meningitis. Serotypes of group B streptococcus other than type III caused more than half of neonatal group B streptococcal disease and mortality, suggesting that an optimal vaccine preparation must be multivalent. Of the organisms evaluated, group B streptococcus was the second most common cause of invasive disease in persons greater than 5 years old.

To determine the morbidity and mortality due to listeriosis in the United States, the authors undertook an active surveillance project in 1986 to identify all cases in which Listeria monocytogenes was isolated from cultures of ordinarily sterile sites in a population of 34 million persons. The authors estimated that at least 1,700 cases of listeriosis and 450 deaths occurred in the United States in 1986; 27% of these cases occurred in pregnant women, with 22% of perinatal cases resulting in stillbirths or neonatal deaths. The risk of listeriosis in adults (0.5 per 100,000 population) was similar in all regions studied; the incidence of perinatal listeriosis was three times higher in Los Angeles County, California, than in the other areas (24.3/100,000 live births vs. 7.8/100,000 live births). Geographic variation may have resulted from underdiagnosis of perinatal listeriosis in five of the study areas. Multilocus electrophoretic enzyme typing was useful for elucidating the molecular epidemiology of L. monocytogenes; perinatal listeriosis was significantly associated with one group of related strains. Multilocus electrophoretic enzyme typing also identified three clusters representing possible common-source outbreaks. These findings document the substantial morbidity due to listeriosis in the United States; to the extent that sporadic listeriosis is foodborne, this morbidity could be reduced by appropriate preventive measures, particularly in persons known to be at increased risk of infection.

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