Usefulness of porA sequencing in distinguishing sporadic and linked cases of serogroup B invasive meningococcal disease in Suffolk, United Kingdom, December 2009 to January 2010

A cluster of three fatal cases of invasive meningococcal disease due to Neisseria meningitidis serogroup B in a town in Suffolk, United Kingdom, during December 2009 to January 2010 was reported to the local Health Protection Unit. This paper describes the investigation undertaken to identify any potential epidemiological links among the cases, to determine if this was an outbreak and to consider whether to implement community-wide interventions and control measures. Case epidemiological information in addition to serogroup and genosubtyping (porA gene sequencing) data of the infecting organism was gathered on all cases in this reported cluster. Genosubtyping was also retrospectively requested for all serogroup B cases confirmed in Suffolk during 2009. Extensive investigation failed to establish an epidemiological link among the cluster of fatal cases of serogroup B invasive meningococcal disease in Suffolk. By demonstrating a number of distinct strains, the genosubtyping of isolates proved to be useful in the public health management of this incident by serving to exclude a community outbreak and preventing unnecessary mass chemoprophylaxis.