Table I.

Demographic, epidemiological, and genomic features of the Ward A outbreak

Variable	Cluster One	Cluster Two	Total
Size of epidemiological outbreak
Total	21	17	38
Patients	21	9	30
Healthcare workers	0	8	8
Patients	N = 21	N = 9	N = 30
Demographics
Median age (years)	82.5	83.7	82.5
Female	2 (9.5%)	0	2 (6.7%)
Context of positive result
Before transferring to Ward A	3 (14.3%)	0	3
On Ward A	6 (28.6%)	8 (88.9%)	14
On another ward	1 (4.8%)	0	1
On admission to hospital post-exposure	11 (52.4%)	1 (11.1%)	12
Reason for testing
Admission testing on Ward A	0	1 (11.1%)	1
Admission testing in A&E	3 (14.3%)	0	3
Developed symptoms on Ward A	6 (28.6%)	0	6
Screening on Ward A post-exposure	0	7 (77.8%)	7
Screening in A&E post-exposure	11 (52.4%)	1 (11.1%)	12
Screening to facilitate discharge	1 (4.8%)	0	1
Public Health England definitionsa
‘definite healthcare-associated’	1	1	1
‘probable healthcare-associated’	3	3	6
‘indeterminate healthcare-associated’	3	3	6
‘community-acquired’	0	1	1
No. of patients readmitted
After contact on Ward A	9	1	10
After household contact	2	0	2
Time from Ward A discharge to positive PCR	12.9	7.2
30-day outcome
Death	4 (19.0%)	1 (12.5%)	5 (16.7%)
Staff	N = 0	N = 8	N = 8
No. of asymptomatic PCR-positive staff	0	5	5
Genomic investigation
No. of samples sequenced	13	6	19
Sample source	All patients	2 patients 4 staff	15 patients 4 staff
Median no. of SNPs different	9	0	11
No. of identical genomes	2	5	7
No. of genomes ≤2 SNPs different	10b	6	16
No. of samples clustered at T = 3	6	5	11 (6 + 5)

PCR, polymerase chain reaction; SNP, single nucleotid polymorphism.

^aPublic Health England definitions for ‘healthcare-associated infections’ were applied to patients detected to be SARS-COV-2 positive during their admission (‘definite’: first positive >15 days after admission; ‘probable’: first positive 8–14 days after admission; ‘indeterminate’: first positive 2–7 days after admission).

^bComprising two groups of seven and three persons.