Table 5.

Start and stop weeks of influenza season using various definitions from 1986–87 to 1990–91 influenza seasons by United States regions. Patients in the study were enrolled from a study site within one of the four regions.

Region	Year	First last isolate		10% moving average		5% moving average		5% all isolates
		Start	Stop	Start	Stop	Start	Stop	Start	Stop
Central	86–87	49	17	51	5	50	9	51	7
Northeast		44	11	50	5	49	6	50	4
South		45	16	53	9	51	10	1	6
West		45	8	51	5	48	6	52	5
Central	87–88	46	22	4	18	3	21	4	13
Northeast		1	22	7	14	6	23	8	13
South		50	25	4	14	3	14	4	13
West		52	20	2	3	1	9	2	11
Central	88–89	47	19	2	12	1	15	3	10
Northeast		47	18	2	18	1	18	4	10
South		50	19	51	15	51	20	3	11
West		51	17	8	10	4	13	3	13
Central	89–90	47	17	51	11	50	12	52	9
Northeast		48	21	1	11	52	12	2	10
South		48	12	50	12	50	13	51	8
West		46	11	3	6	52	9	51	8
Central	90–91	48	19	5	14	3	14	4	13
Northeast		45	22	3	10	50	17	3	8
South		40	19	1	16	51	19	3	8
West		52	21			5	9	5	12