Table 5. Case-case comparisons of community SARS patients, Guangdong, China, November 2002–April 2003, according to contact history and onset date^a.

Exposure (in previous 2 weeks)	No contact history (n = 406)		Contact history (n = 103 )			Early onsetb (n = 19)c		Late onsetb (n = 387)c
	Yes	No	Yes	No	OR (95% CI)	Yes	No	Yes	No	OR (95% CI)
Visited hospital	17	70	22	13	6.83 (2.89 to 6.73)	0	10	45	169	0.00 (0.00 to 1.36)
Visited by a friend	4	71	1	17	1.04 (0.04 to 8.93)	0	1	4	70	0.00 (0.00 to 337)
Regular hand washing	122	15	44	3	1.80 (0.53 to 8.10)	4	1	118	14	0.48 (0.06 to 12.55)
Travel history	45	179	13	62	0.83 (0.41 to 1.63)	0	10	45	169	0.00 (0.00 to 1.36)
Animal contact	37	262	13	56	1.64 (0.80 to 3.25)	1	3	36	259	2.39 (0.09 to 23.02)
Visited produce market	9	79	1	19	0.41 (0.02 to 2.75)	0	1	9	69	0.00 (0.00 to 148)
Lives near produce market	89	169	19	43	0.84 (0.45 to 1.52)	5	0	84	169	Undef. (2.39 to Undef.)
Lives near poultry or livestock farm	6	252	3	59	2.13 (0.42 to 8.81)	0	19	6	247	0.00 (0.00 to 40.15)

^aSARS, severe acute respiratory syndrome; CI, confidence interval; OR, odds ratio.
^bDefined as November 1, 2002–January 31, 2003 for early onset; February 1, 2003–April 30, 2003 for late onset.
^cCases with no contact history and for whom case investigation data are available.