Volume 17, Number 8—August 2011
Research
Early Warning System for West Nile Virus Risk Areas, California, USA
Table 4
Year and activity | % (No.) agencies | Prediction rate |
Prediction rate (excluding outlier)† |
|||||
---|---|---|---|---|---|---|---|---|
% Cases (no./total) | Rate ratio (95% CI) | p value | % Cases (no./total) | Rate ratio (95% CI) | p value | |||
2006 | ||||||||
Larviciding | 10.06 (2.45–41.32) | 0.001 | NA | NA | ||||
Yes | 85.0 (34) | 41.9 (52/124) | 41.9 (52/124) | |||||
No | 15.0 (6) | 4.2 (2/48) | 0 (0/5) | |||||
Adulticiding | 10.91 (2.65–44.88) | 0.001 | NA | NA | ||||
Yes | 74.4 (29) | 39.7 (48/121) | 39.7 (48/121) | |||||
No |
25.6 (10) |
3.6 (2/55) |
0 (0/12) |
|||||
2007 | ||||||||
Larviciding | 10.16 (1.41–73.00) | 0.021 | 5.63 (0.66–48.15) | 0.115 | ||||
Yes | 72.2 (13) | 56.4 (79/140) | 31.3 (5/16) | |||||
No | 27.8 (5) | 5.6 (1/18) | 5.6 (1/18) | |||||
Adulticiding | 0.37 (0.15–0.91) | 0.031 | 1.88 (0.22–16.05) | 0.566 | ||||
Yes | 47.1 (8) | 20.8 (5/24) | 20.8 (5/24) | |||||
No | 52.9 (9) | 56.4 (75/133) | 11.1 (1/9) |
*DYCAST, Dynamic Continuous-Area Space-Time; CI, confidence interval; NA, not applicable. Agencies were asked whether they used DYCAST to assist larviciding, adulticiding; agencies that did not respond to survey, as well as answers of “Don’t know” (2006: larviciding: n = 2, adulticiding: n = 4) and missing data (2006: larviciding: n = 5, adulticiding: n = 4; 2007: adulticiding: n = 1), were omitted from analysis. Number of analyzed agencies with reported human cases: 2006: larviciding: “Yes”: n = 21, “No”: n = 4; adulticiding: “Yes”: n = 19, “No”: n = 7; 2007: larviciding: “Yes”: n = 6, “No”: n = 4; adulticiding: “Yes”: n = 5, “No”: n = 4. p values are 2 tailed; statistically significant associations (p<0.05) are in boldface.
†Outlier, with respect to total number of cases, was a single agency with 43 and 124 cases in 2006 and 2007, respectively.
1Current affiliation: Brown University, Providence, Rhode Island, USA.
2Current affiliation: University of British Columbia, Vancouver, British Columbia, Canada.