Table 3.

Pertussis incidence in different regions

	No. of cases	Incidence (per 100 000)
Region		Symptom surveillance	Hospital screening	Fold difference
Hongqiao	45	23·89	0	—
Beichen	18	9·95	2·89	3·44
Hangu	50	45	1·8	25
Total	113	23·52	1·45	16·22