Influence of age on serogroup distribution of endemic meningococcal disease.

The age distribution of 126 infants and children with disseminated meningococcal disease hospitalized consecutively in Houston between January 1977 and June 1979, and between January 1981 and June 1981 was analyzed and compared with that in the United States as a whole and to that during outbreaks of group B disease in North America and epidemics of group C disease in South America. Eighty-one (64.3%) isolates from Houston cases were serogroup B and 37 (29.4%) were serogroup C Neisseria meningitidis. Children with serogroup C disease were significantly older than those with group B disease (P = .017). Of the children with serogroup B infections, 33% were less than 12 months of age and 8.6% were less than 3 months of age. Of those with serogroup C disease, only 2.7% were less than 3 months of age and the majority (73%) were more than 2 years of age. These age distributions are similar to those reported for the entire United States during endemic periods. In contrast, focal outbreaks of group B meningococcal infection occurred in populations that were significantly older (0.02 greater than P less than .05). Similarly, epidemic disease in South America due to serogroup C strains also occurred in older children when compared with the occurrence of endemic group C disease in the United States (P = .02).