Meningococcal disease in urban south western Sydney, 1990–1994

Background: There has been a sustained increase in incidence of meningococcal disease throughout Australia since 1987. In south western Sydney the incidence is higher than the national rate and a cluster of cases occurred in 1991 resulting in a widespread vaccination programme. Aims: To investigate the clinical demographics of patients with meningococcal disease treated in south western Sydney, and to differentiate meningococcal strains to understand better the epidemiology in this urban setting. In addition, to investigate whether delays in diagnosis of meningococcal disease and institution of appropriate treatment were occurring. Methods: Retrospective classification of notified cases as meningitis, septicaemia, meningitis/septicaemia, and other syndromes. Clinical information recorded to establish patterns of disease, delays in diagnosis and appropriate treatment, and outcome. Microbiological classification of organisms isolated by serogroup, serotype and subtype. Results: Meningococcal disease primarily affects young children in winter months in south western Sydney, with a secondary peak of incidence in the 15–20 year old age group. 20.7% presented with meningitis only, 22.4% with septicaemia only, and 53.4% with meningitis/septicaemia. There was a delay in diagnosis and institution of appropriate treatment of more than two hours in 21/58 (36.2%) patients including three of the six who died. No patient had received a parenteral antibiotic prior to coming to hospital - 18.9% had received an oral antibiotic. The use of antibiotics before diagnostic lumbar puncture decreased the number of positive CSF cultures. However, in all but one patient with negative cultures there was other microbiological evidence of meningococcal disease. The mortality rate was highest (30.8%) in patients with septicaemia only, 6.5% in patients with meningitis/septicaemia and 0% in patients with meningitis only. Serogroup C was the predominant organism in all age groups. The predominant serotype was 2b (80% of serogroup C isolates). Subtypes were more variable but P1.2 occurred in 66.7% of serogroup C strains. Conclusions: There is a need for more education in our Health Area to improve the time taken to diagnose and institute appropriate treatment. The predominance of serogroup C is unusual in urban Australia where national data show serogroup B organisms predominate. Meningococci of phenotype C:2b:Pl.2 have continued to cause disease in our Health Area for the past five years. This phenotype is uncommon in other areas of Australia.