Fourteen cases of meningococcal disease (MD) occurred in August–September 1996 in western Sydney, Australia. Seven of the 10 young adults affected had a direct or indirect link with a local nightclub. Ten of 11 systemic meningococcal isolates had the phenotype C[ratio ]2a[ratio ]P1.5 and showed close genetic relationship by pulsed-fleld gel electrophoresis (PFGE). Organisms of this phenotype have not previously caused outbreaks in Australia, but have been associated with outbreaks and hyperendemic serogroup C MD in Europe, Canada, and the United States.

This is the largest cluster of serogroup C MD reported in urban Australia, and the first involving a nightclub. The strain differentiation results were available rapidly enough to augment epidemiological investigations on a daily basis. Public health staff could thus establish links between cases quickly, follow the spread of new cases in the community, give accurate information to health officials and the press, and utilize existing knowledge about the characteristics of this phenotype to predict likely developments during the outbreak and afterwards. The strain differentiation data was also very helpful when the role of vaccination was considered, and existing guidelines on the management of outbreaks of MD could be used effectively for the first time in western Sydney.