Epidemiology of meningococcal disease in Denmark 1974-1999: contribution of the laboratory surveillance system.

The Danish meningococcal disease laboratory surveillance system was established in 1974, based on close collaboration between local Departments of Clinical Microbiology and the Reference Laboratory at Statens Serum Institut. The completeness of the clinical notification system integrated with the laboratory surveillance system has been estimated to be more than 95%. Overall 4257 (79%) of 5356 cases of meningococcal disease notified during 1974-1999 were confirmed by culture of Neisseria meningitidis. The proportion of culture-confirmed cases ranged from 70% in 1989 to 89% in 1980. Only 26 patients (0.6%) with culture-confirmed meningococcal disease were not notified. Serological phenotype and susceptibility to penicillin and sulphonamide were determined for all isolates. Multilocus enzyme electrophoresis and/or DNA-based analyses were used for the assessment of clusters and outbreaks. Meningococcal antibody tests and counter-immunoelectrophoresis were used for the ascertainment of suspected cases. These combined systems allowed timely and reliable management of outbreaks and identification of clusters.