No. of new episodes	Days at risk	Incidence/100 days at risk	95% CIa	p valueb
Respiratory symptoms
Total	1,547	33,228	4.66	4.43, 4.89
Sex					0.625
Boys	685	14,508	4.72	4.38, 5.09
Girls	862	18,720	4.60	4.31, 4.92
Age (mo)					<0.001
<5	201	6,870	2.93	2.55, 3.36
6–11	471	8,439	5.58	5.10, 6.11
12–17	462	8,838	5.23	4.77, 5.73
18–23	413	9,081	4.55	4.13, 5.01
Calendar periodsc					0.081
Jan–Mar	393	8,957	4.39	3.97, 4.84
Apr–Jun	391	8,954	4.37	3.95, 4.82
Jul–Sep	403	7,944	5.07	4.60, 5.59
Oct–Dec	360	7,373	4.88	4.40, 5.41
Fever, reported
Total	1,106	63,584	1.74	1.64, 1.85
Sex					0.538
Boys	503	29,505	1.70	1.56, 1.86
Girls	603	34,079	1.77	1.63, 1.92
Age (mo)					<0.001
<5	112	10,059	1.11	0.93, 1.34
6–11	371	16,689	2.22	2.01, 2.46
12–17	358	18,217	1.97	1.77, 2.18
18–23	265	18,619	1.42	1.26, 1.61
Calendar periodsc					<0.001
Jan–Mar	309	16,609	1.86	1.66, 2.08
Apr–Jun	230	16,921	1.36	1.19, 1.55
Jul–Sep	314	15,326	2.05	1.83, 2.29
Oct–Dec	253	14,728	1.72	1.52, 1.94
Diarrhea, reported
Total	523	69,255	0.76	0.69, 0.82
Sex					0.016
Boys	268	31,833	0.84	0.75, 0.95
Girls	255	37,422	0.68	0.60, 0.77
Age (mo)					<0.001
<5	48	10,623	0.45	0.34, 0.60
6–11	158	18,705	0.84	0.72, 0.99
12–17	179	19,981	0.90	0.77, 1.04
18–23	138	19,946	0.69	0.59, 0.82
Calendar periodsc					<0.001
Jan–Mar	215	17,423	1.23	1.08, 1.41
Apr–Jun	50	18,516	0.27	0.20, 0.36
Jul–Sep	101	17,419	0.58	0.48, 0.70
Oct–Dec	157	15,897	0.99	0.84, 1.15
aCI, confidence interval. bLikelihood-ratio test. cMonths accumulated in monitoring period (July 30, 1996–August 13, 1998).