Table 2. Characteristics of domestic and non-domestic clusters of STEC O157:H7, England, 2013–2017.

Domestic lineage, clade or cluster Sub-lineages Ic and IIb and clusters within sub-lineages IIc and I/II	Non-domestic lineage, clade Sub-lineages Ia, Ib and IIa and I/II
Characteristics
Common in domestic dataset	Rare in domestic dataset
Short branch lengths (low level diversity) between clusters and clades representing frequent sampling of a restricted pool	Longer branch lengths (high level diversity) between clusters and clades representing infrequent sampling of the global pool
High frequency of domestic animal isolates sampled during prevalence studies and sequenced isolates are included in the dataset	Domestic animal isolates not present
Cases do not report recent travel outside the UK before onset of symptoms	High frequency of cases reporting recent travel before onset of symptoms
Cases from outbreaks known to be associated with domestically produced food,	Cases from outbreaks known to be associated with imported food, Outbreak Scenario 2
Cases associated with local environmental exposures, such as petting farms or parks	Cases not associated with local environmental exposures

STEC: Shiga toxin-producing Escherichia coli; UK: United Kingdom.