Space-Time Cluster Analysis of Invasive Meningococcal Disease

Abstract

Clusters are recognized when meningococcal cases of the same phenotypic strain (markers: serogroup, serotype, and subtype) occur in spatial and temporal proximity. The incidence of such clusters was compared to the incidence that would be expected by chance by using space-time nearest-neighbor analysis of 4,887 confirmed invasive meningococcal cases identified in the 9-year surveillance period 1993–2001 in the Netherlands. Clustering beyond chance only occurred among the closest neighboring cases (comparable to secondary cases) and was small (3.1%, 95% confidence interval 2.1%–4.1%).

Keywords

• Neisseria meningitidis
• invasive meningococcal disease
• outbreak
• cluster analysis
• space-time analysis
• secondary cases