Spatial-temporal epidemiology of human Salmonella Enteritidis infections with major phage types (PTs 1, 4, 5b, 8, 13, and 13a) in Ontario, Canada, 2008–2009

Table 4 Clusters of Salmonella Enteritidis cases with the six most frequent phage types in Ontario, Canada, 2008–2009

Phage type (N)	Annual cases per 100,000	Cluster type	Region	Time frame (Year/Month)	Observed	Expected	O/E	RR	P-value
PT 1 ( N = 132)	0.05	Space-time	North West, North East, Eastern, Central East	2008/1 to 2008/2	20	5.17	3.87	4.38	≤0.001
		Space-time	Central West	2008/1 to 2008/5	16	5.24	3.05	3.33	0.046
		Temporal	All	2008/1 to 2008/3	40	16.36	2.38	3.07	0.001
PT 4 ( N = 76)	0.03	Space-time	Eastern, Central East	2008/2 to 2008/4	15	3.89	3.85	4.55	0.010
PT 4 ( N = 76)	0.03	Temporal	All	2008/1 to 2008/11	51	34.67	1.47	2.43	0.009
PT 5b ( N = 83)	0.03	Spatial	Central West	NA	29	15.93	1.82	2.26	0.003
		Space-time	Central West	2008/9 to 2009/4	17	5.27	3.22	3.80	0.016
		Temporal	All	2008/12 to 2009/3	29	13.77	2.11	2.70	0.002
PT 8 ( N = 397)	0.20	Spatial	North West	NA	22	7.37	2.98	3.10	≤0.001
		Space-time	North West	2009/2 to 2009/5	15	1.20	12.46	12.91	≤0.001
		Space-time	South West	2008/9 to 2008/12	21	8.11	2.59	2.68	0.046
PT 13 ( N = 198)	0.08	Spatial	Toronto	NA	74	40.71	1.82	2.31	≤0.001
		Space-time	Toronto	2008/4 to 2008/10	40	11.87	3.37	3.97	≤0.001
		Temporal	All	2008/4 to 2008/5	29	16.46	1.76	1.89	0.051
PT 13a (N = 218)	0.08	Spatial	Toronto	NA	63	44.70	1.41	1.58	0.018
		Space-time	Toronto	2009/10 to 2009/12	18	5.64	3.19	3.39	0.018
		Temporal	All	2008/7 to 2008/10	63	36.51	1.73	2.02	0.001

N = number of S. Enteritidis cases with the phage type. Results based on discrete Poisson models using the SaTScan™ software. Study period: January 1, 2008 to December 31, 2009. Time aggregation units: month. Time aggregation length: 1 month. Circular scanning window size: up to 50 % of the population at risk and/or 50 % of time the study period. Confounders controlled for: age (0–9, 10–24, 25–34, 35–49, ≥ 50 years) and sex. Criteria for reporting secondary clusters: no geographical overlap. Type of clusters investigated: high rate only. NA = not applicable. O/E = observed divided by expected. RR = relative risk. Significance level: p ≤ 0.05

ISSN: 1471-2458