Table 4. Ratio of West Nile neuroinvasive disease (WNND) to infection by age-group.

Age (years)	WNND cases	Population in study area	Ratio of WNND to infection (95% CI)	Population in affected areas	Ratio of WNND to infection (95% C.I.) (of affected areas)—ELISA	Ratio of WNND to infection (95% C.I.) (of affected areas)—PRNT
80+	84	583,334	1:465 (1:724, 1:296)	355,156	1:283 (1:440, 1:180)	1:213 (1:379, 1:109)
65–79	182	1,525,518	1:385 (1:653, 1:302)	1,061,744	1:268 (1:338, 1:210)	1:247 (1:322, 1:187)
55–64	47	1,286,137	1:301 (1:556, 1:186)	764,510	1:179 (1:330, 1:111)	1:148 (1:303, 1:64)
25–54	54	4,671,656	1:1125 (1:1260, 1:921)	3,124,653	1:752 (1:843, 1:616)	1:506 (1:654, 1:392)
0–24	11	2,749,641	1:4749 (1:6509, 1:4051)	1,470,553	1:2540 (1:3485, 1:2167)	1:1513 (1:1691, 1:1481)
All ages	378	10,816,286	1:601 (1:673, 1:539)	6,776,616	1:376 (1:421, 1:338)	1:276 (1:321, 1:236)