Volume 11, Number 9—September 2005
Research
Dead Crow Density and West Nile Virus Monitoring, New York
Millicent Eidson*
, Kate Schmit*, Yoichiro Hagiwara*, Madhu Anand*, P. Bryon Backenson*, Ivan Gotham*, and Laura Kramer*
, Kate Schmit*, Yoichiro Hagiwara*, Madhu Anand*, P. Bryon Backenson*, Ivan Gotham*, and Laura Kramer*
Table 2
Risk for West Nile virus disease in counties with elevated dead crow density (DCD) in the 2 weeks before disease onset*
| Counties with elevated DCD† | 2001 RR (95% CI) | 2002 RR (95% CI) | 2003 RR (95% CI) | 2001–2003 RR (95% CI) |
|---|---|---|---|---|
| 2 weeks before onset | 8.6 (1.8–41.8) | 2.2 (1.1–4.6) | 5.4 (2.1–14) | 3.5 (2.0–6.0) |
| 1 or 2 weeks before onset | 7.9 (2.9–19.1) | 2.3 (1.1–4.8) | 6.5 (2.6–16.3) | 3.8 (2.2–6.6) |
| 0, 1, or 2 weeks before onset | 7.6 (1.6–36.8) | 2.0 (0.95–4.4) | 5.3 (2.2–12.8) | 3.4 (1.9–5.9) |
*Versus residents of counties without elevated DCD in the previous 2 weeks; risk is calculated for exposure to elevated DCD only 2 weeks before, 1 or 2 weeks before, and during the same week or 1 or 2 weeks before week of onset. SAS provides risk estimates by 2 methods; because zero values occur in 2×2 tables for some weeks, we report results by the adjusted logit method, which uses a 0.5 correction for zero-value cells. RR, relative risk; CI, confidence interval.
†Weekly DCD >0.1.
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