Table 1.

Descriptive Characteristics of Enrolled Patients With Medically Attended Acute Respiratory Infections by Case/Control Status

Characteristics	Influenza Cases		Influenza-Negative Controls		P Value
	N = 1040	%	N = 3717	%
Study community
Marshfield, WI	219	21	1535	41	<.001
Rochester, NY	145	14	350	9
Southeast, MI	377	36	864	23
Nashville, TN	299	29	968	26
Enrollment site
Outpatient	760	73	2638	71	<.001
Inpatient	112	11	634	17
Emergency Dept	168	16	445	12
Sex
Male	473	45	1678	45	.84
Female	567	55	2039	55
Age groups
6 months–2 years	96	9	688	19	<.001
3–8 years	271	26	767	20
9–18 years	141	14	472	13
19–49 years	341	32	957	26
50–64 years	126	12	473	13
65–74 years	38	4	177	5
≥75 years	27	3	183	5
Race
White	583	56	2586	70	<.001
Black	258	25	651	18
Other	199	19	480	13
Insurance status
Not insured	87	8	200	5	.002
Private insurance	660	63	2466	66
Public insurance	293	28	1051	28
High-risk condition
No	712	68	2320	62	<.001
Yesa	328	32	1397	38
Onset to test
<3 days	477	46	1596	43	<.001
3–4 days	397	38	1313	35
5–7 days	166	16	808	22

^a Presence of at least 1 condition among high-risk–respiratory; high-risk–cardiovascular; high-risk–diabetes; and high-risk–other diseases.