Meningococcal disease--management of serogroup C clusters in a hyperendemic area

Recent evidence in Ireland highlights an increased incidence of meningococcal disease, with group B the prominent serogroup. However, in developed countries, 'clusters 'are predominantly group C. To retrospectively analyse all patients with meningococcal disease in the North Eastern Health Board (NEHB) Region (circa 300,000 population) from January 1997 to December 1998 inclusively, and to highlight the occurrence of two 'clusters' of Group C meningococcal disease, one in Drogheda and the other in Monaghan (both of whom received national media attention). We studied clinical, laboratory (including PCR) and epidemiological data on all patients in the NEHB with a diagnosis of meningococcal disease. Blood for PCR (Polymerase Chain Reaction) was sent to the National Meningococcal Reference Laboratory on all suspected cases. Details of two 'clusters' were studied in depth from an epidemiological perspective. 131 patients with meningococcal disease were notified, with three deaths of 53 notifications in 1997 (7.5% mortality) and six deaths of 78 notifications in 1998 (9.8% mortality). The rate of meningococcal disease per 100,00 in 1997 was 13.1 and rose to 18.6 in 1998. This contrasts with a national average of 8.5 per 100,00 for the Republic of Ireland in 1997. Age peaks occurred in those under one year old and between 14-16 years old, with seasonal peaks in the winter and spring months. In 1997, 57.5% were group B and 35% were group C, with 7.5% not grouped. In 1998, 60.3% were group B and 39.7% were group C. There were two linked cases in Drogheda, with both attending a local national school. Both were confirmed group C disease. In Monaghan, in January 1998, a cluster of four cases of group C disease occurred over a 48 hour period. All were males, ranging in age from 11-16 years. Of the four, one died and one received intensive care treatment in a children's hospital. The cluster received intense local and national media attention. One week later, a fifth case of group C disease occurred in Monaghan and this 10 year old boy made an uneventful recovery. The high endemic rate of meningococcal disease is striking, with a four fold rise over the past five years. Clusters of serogroup C meningococcal disease will be of historical interest now that new conjugate C vaccines are incorporated into the vaccination program.