Table 2.

Age-specific fever episodes and incidence of dengue infection and illness in children, Sri Lanka^*

Age (years)	No. children	Fever episodes		New dengue infections			Incidence of infection per 100 children	Incidence of disease per 100 children
		Total	Mean/child	Total	Inapparent	Apparent
< 1	51	31	0.6	1	0	1	1.96 (0.05–10.45)	1.96 (0.05–10.45)
1–3	196	252	1.3	27	15	12	13.78 (9.28–19.41)	6.12 (3.20–10.45)
4–6	191	174	0.9	13	11	2	6.81 (3.67–11.36)	1.05 (0.13–3.73)
7–9	225	137	0.6	15	6	9	6.67 (3.78–10.76)	4.00 (1.85–7.46)
10–12	136	87	0.6	11	8	3	8.09 (3.25–16.03)	2.21 (0.46–6.31)
Total	799	681	0.9	67	40	27	8.39 (6.56–10.53)	3.38 (2.24–4.88)

^*Values in parentheses are 95% confidence intervals. Clinically apparent dengue infections were diagnosed by performing paired serologic analysis and polymerase chain reaction on acute-phase and convalescent-phase serum samples obtained from febrile children. Total dengue infections over the study year were detected by testing paired baseline and end of year samples by IgG enzyme-linked immunosorbent assay and neutralization test. Children who were infected but not identified as having apparent cases were designated as having inapparent cases.