Table 2.

Number of ill and healthy people who ate certain food items, attack rates, and relative risk for each food item – outbreak of salmonellosis, Oswego, New York, 1940

	Number of persons who ate item			Number of persons who did not eat item			Relative risk
	Ill	Total	Attack rate (%)	Ill	Total	Attack rate (%)
Baked ham	29	46	63	17	29	59	1.07
Spinach	26	43	60	20	32	62	0.97
Potatoes	23	37	62	23	37	62	1.00
Jellies	16	23	70	30	52	58	1.21
Rolls	21	37	57	25	38	66	0.86
Coffee	19	31	61	27	44	61	1.00
Cake	27	40	68	19	35	54	1.26
Ice cream	43	54	80	3	21	14	5.71a

^ap < 0.001.

Centers for Disease Control and Prevention, 2004. Steps of an Outbreak investigation. Available at: http://www.cdc.gov/excite/classroom/outbreak/steps.htm (accessed June 2008).