Table 2. Summary of distinct outbreak events for the Glasgow and Sheffield datasets, according to standard PHE definition and with the addition of sequence data.

	Glasgow data	Sheffield data
n HOCI cases	125	201
n ward locations	44	38
Sequence matches per HOCI case
n sequence matches from same ward, median (IQR, range)	1 (0–5, 0–12)	1 (0–4, 0–18)
n sequence matches from rest of hospital, median (IQR, range)	3 (1–8, 0–52)	27 (5–52, 0–150)
Standard PHE definition of outbreak event
HOCI cases part of ward outbreak event, n (%)	95 (76.0)	184 (91.5)
n ward outbreak events	17	24
n HOCI cases per ward outbreak event, median (IQR, range)	4 (2–8, 2–17)	5 (3.5–10.5, 2–28)
Days from first to last case in outbreak, median (IQR, range)	8 (6–15, 0–31)	18 (13–34, 3–68)
n wards with more than one distinct outbreak event	0	0
Outbreak events with sequence linkage
HOCI cases part of ward outbreak event, n (%)	85 (68.0)	140* (69.7)
n ward outbreak events	16	33
n HOCI cases per ward outbreak event, median (IQR, range)	3.5 (2–8, 2–16)	3 (2–4, 1–19)
Days from first to last case in outbreak, median (IQR, range)	6 (4–9, 0–15)	4 (2–8, 0–17)
n wards with more than one distinct outbreak event	0	9†

* Includes two HOCIs which each showed a close sequence match to another case on the same ward with interval from admission to sample date ≤2 days.

†In three wards, there were three genetically distinct outbreak events.

HOCI: hospital onset COVID-19 infection; IQR: interquartile range; PHE: Public Health England.