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Volume 19, Number 6—June 2013

Research

Active Surveillance for Influenza A Virus among Swine, Midwestern United States, 2009–2011

Cesar A. Corzo, Marie CulhaneComments to Author , Kevin Juleen, Evelyn Stigger-Rosser, Mariette F. Ducatez, Richard J. Webby, and James F. Lowe
Author affiliations: University of Minnesota, Saint Paul, Minnesota, USA (C.A. Corzo, M. Culhane, K. Juleen); St. Jude Children’s Research Hospital, Memphis, Tennessee, USA (E. Stigger-Rosser, M.F. Ducatez, R.J. Webby); Carthage Veterinary Services, Carthage, Illinois, USA (J.F. Lowe)

Main Article

Table 4

Relationships between clinical signs with subtype and season among pigs tested for influenza virus, midwestern United States, June 2009–December 2011*

Variable Estimate Odds ratio (95% CI) p value
Season†
Intercept 0.234 NA 0.65
Fall (referent) NA NA NA
Spring –0.411 0.6 (0.1–2.5) 0.53
Summer –0.410 0.6 (0.1–2.4) 0.53
Winter
0.361
1.4 (0.3–6.7)
0.63
Influenza virus subtype‡
Intercept 1.7 NA 0.95
H1N1 (referent) NA NA NA
H1N2 –1.381 0.5 (0.1–2.0) 0.96
H3N2 –1.476 0.5 (0.09–2.5) 0.95
H1N2v –2.105 0.2 (0.03–2.0) 0.93
H3N2v 9.541 NA 0.95
H1N1pdm09 –1.582 0.4 (0.1–1.7) 0.95
Mixed infection –2.210 0.2 (0.04–1.3) 0.93

*Logistic regression univariate analysis; NA, not applicable.
†Generalized χ2 divided by degrees of freedom = 0.96.
‡Likelihood ratio χ2 (6) = 6.01 df, p = 0.42.

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