Table 2.

Comparison of WNV-to-WNND ratios, by gender and age, from donors with evidence of infection in 2012 and those described in the Carson et al. [4] serosurvey

Age group, years	No. donors	WNV 2002–2012	WNV 2012	WNV seroprev, % 2012 (95% CI)	Total pop.	WNV-infected population	No. WNND cases	(A) Infections:1 WNND (95% CI)	(B) Infections:1 WNND (95% CI) [4]	A:B (95% CI)
Male	2731	84	39	1·4 (1·0–2·0)	2 204 852	31 486	202	156 (109–222)	220 (185–263)	0·72 (0·49–1·06)
16–24	299	6	2	0·7 (0·1–3·6)	412 351	2758	11	251 (45–1359)	719 (385–1250)	0·35 (0·06–1·96)
25–44	819	20	9	1·1 (0·4–2·6)	872 522	9588	41	234 (97–559)	356 (238–556)	0·71 (0·28–1·83)
45–64	1290	44	23	1·8 (1·0–3·1)	690 617	12 313	75	164 (94–286)	248 (178–345)	0·66 (0·36–1·22)
⩾65	323	14	5	1·6 (0·5–4·8)	229 362	3550	75	47 (15–147)	50 (39–66)	0·96 (0·27–3·35)
Female	2240	55	30	1·3 (0·9–2·0)	2 316 862	31 029	147	221 (140–316)	291 (227–370)	0·68 (0·44–1·05)
16–24	322	3	2	0·6 (0·1–3·4)	400 255	2486	5	243 (44–1319)	1231 (11–3333)	0·40 (0·07–2·29)
25–44	798	20	12	1·5 (0·7–3·2)	891 854	13 411	36	239 (99–571)	330 (204–556)	1·13 (0·48–2·68)
45–64	947	26	12	1·3 (0·6–2·7)	721 032	9137	52	171 (98–298)	387 (238–625)	0·45 (0·20–1·02)
⩾65	173	6	4	2·3 (0·6–7·9)	303 721	7022	54	63 (20–194)	61 (41–90)	2·10 (0·45–9·69)
Total	4971	139	69	1·4 (1·1–1·8)	4 521 714	62 764	349	180 (142–227)	244 (213–286)	0·72 (0·56–0·93)
Adjusted total*			91†	1·8 (1·5–2·2)		82 775		238 (192–290)		0·96 (0·76–1·20)

WNV, West Nile virus; WNND, WNV neuroinvasive disease; CI, confidence interval.

The total number of WNND cases does not include the six reported individuals aged <16 years.

^*Adjusted total accounts for the estimated IgM fall-off, as described in the Methods section and text.

^†Estimated number of WNV 2012 infections accounting for IgM fall-off, as described in the Methods section and text.