Table 2. Clinical characteristics for the influenza A (H1N1) cases in the early stage of the epidemic in mainland China.

Symptom	Cases			χ2a	P
	Total cases (N = 420)	Imported cases(N = 297)	Second-generation cases (N = 85)
Fever	341 (81.2)	264 (88.9)	65 (76.5)	8.53	0.00
Cough	168 (40.0)	108 (36.4)	49 (57.6)	12.37	0.00
Sore throat	148 (35.2)	85 (28.6)	52 (61.2)	30.45	0.00
Runny nose	41 (9.7)	35 (11.8)	6 (7.1)	1.54	0.21
Headache	23 (5.5)	19 (6.4)	4 (4.7)	0.33	0.56
Fatigue	23 (5.2)	19 (6.4)	4 (4.7)	0.33	0.56
Muscle aches and pains	18 (4.3)	15 (5.0)	3 (3.5)	0.08	0.77
Expectoration	9 (2.1)	6 (2.0)	3 (3.5)	0.16	0.69
Chills	5 (1.0)	5 (1.7)	0	-	0.59
Vomit	3 (0.7)	2 (0.7)	1 (1.2)	-	0.53
Chest tightness	2 (0.5)	2 (0.7)	0	-	1.00
dizziness	3 (0.5)	2 (0.7)	4 (4.7)	4.59	0.03
Diarrhea	2 (0.5)	1 (0.3)	1 (1.2)	0.89	0.34
Syncope	1 (0.2)	1 (0.3)	0	-	1.00

Note: The data in the brackets are incidences (%); ^a Comparison between imported and second-generation cases; - Fisher’s exact test.