Footnotes

• Contributors All authors were members of the outbreak control team; all authors contributed to early discussions about the format of the paper. KF drafted the first version and all authors contributed to further versions and agreed final content. AW undertook the analysis of enhanced surveillance data and compiled the network diagrams and MC completed the molecular analysis.

• Competing interests None declared.

• Ethics approval All work reported was carried out as part of an outbreak investigation and therefore ethics approval was not required. PHE has authority to collect patient-level data for public health monitoring and infection control under section 251 of the NHS Act 2006. Prior to 2013 permission was granted to the Health Protection Agency, PHE's predecessor organisation, under section 251 by the Ethics and Confidentiality Committee of the National information Governance Board.

• Provenance and peer review Not commissioned; externally peer reviewed.

• Data sharing statement Data held at Public Health England North East; available to appropriate practitioners for internal surveillance purposes only.