[Epidemiological and laboratory criteria in the assessment of meningococcus carrier state]

A study was made of the duration of meningococcus carrier state, immunological indices and group-specific properties of meningococci isolated from them. The periods of meningococcus discharge were studied in 738 persons. Three categories of the carrier state were revealed: a single discharge (67% of the carriers), of average duration (up to 4 weeks), and prolonged. Greater indices of group-specific antibodies (in the passive hemagglutination test) were revealed in the carriers with prolonged presence of meningococci in the nasopharynx. Dynamics of immunological indices and periods of the carrier state formation in the foci of infection permitted to characterize the prolonged carrier state as a latent form of meningococcus infection. A study of the group-specific properties in 1845 strains and comparison of the group-specific pattern of the circulating strains with the epidemic situation indicated that meningococci of group A were not only epidemic, but also more virulent.