Managing meningococcal disease case clusters: art or science?

The epidemiology of meningococcal disease in England and Wales has been subject to regular periodic review and comment. Seasonal and period trends in incidence based upon laboratory confirmed reports and oYcial notifications have been documented for all meningococcal disease and for major serogroups and sub-types. The disease is noted to be commoner in the winter months and among younger age groups, particularly children under two years of age. Since the latter period of the past decade case ascertainment for meningococcal disease has increased. This is believed in part to be attributable to improved notification procedures and reporting practices, particularly in some regions where improved surveillance of meningococcal disease has been undertaken in recent years. However, some increase in incidence seems likely as the number of reported deaths from meningococcal disease have increased despite a fall in the case fatality rate. There has also been a change in the epidemiology of meningococcal disease during the past five years in the UK and elsewhere with an increase in the proportion of Group C strains and a corresponding decrease in the proportion of cases caused by Group B. This change in the proportion of B and C strains causing disease has been accompanied by an upward shift in the age distribution of cases with a greater proportion now occurring in older age groups. 3 However, the most significant eVect on the public health management of meningococcal disease as a result of these changes in the epidemiology has been attributable to the more frequent occurrence of case clusters. Family, nursery, school, university and other institutional case clusters have been reported. Guidelines for the management of such meningococcal case clusters in the UK have been developed for Consultants in Communicable Disease Control (CsCDC) by the Public Health Laboratory Service (PHLS) and Public Health Medicine Environmental Group (PHMEG) Meningococcus Working Group. The guidelines advise that chemoprophylaxis should be considered if two or more probable or confirmed cases occur at the same time within a period of one month and that in addition that vaccination with meningococcal A/C vaccine should be oVered if a vaccine preventable strain is confirmed. The average number of cases in each cluster is small (median 2–5) and the occurrence of clusters remains relatively uncommon, but management may be problematic. We describe two case clusters of meningococcal disease in Liverpool that occurred during the winter of 1998 illustrating some of the practical dilemmas that may be encountered in the management of such case clusters.