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Volume 13, Number 12—December 2007

Swine Workers and Swine Influenza Virus Infections

Gregory C. Gray*Comments to Author , Troy McCarthy*, Ana W. Capuano*, Sharon F. Setterquist*, Christopher W. Olsen†, Michael C. Alavanja‡, and Charles F. Lynch*
Author affiliations: *University of Iowa College of Public Health, Iowa City, Iowa, USA; †University of Wisconsin-Madison School of Veterinary Medicine, Madison, Wisconsin, USA; ‡National Cancer Institute, Bethesda, Maryland, USA;

Main Article

Table 3

Serologic evidence for influenza infections during the 24 months of follow-up

Period N >4-fold increase
Swine influenza (H1N1)
Swine influenza (H1N2)
Human influenza (H1N1)
n Reported ILI,* 
n (%) n Reported ILI,* 
n (%) n Reported ILI,* 
n (%)
Enrollment to 12-mo follow-up 658 26 3 (11.5) 17 7 (41.2) 10 1 (10)
12- to 24--mo follow-up 586 109 18 (16.5) 16 2 (12.5) 19 3 (15.8)
Enrollment to 24-mo follow-up 654 141 31 (22) 23 2 (8.7) 20 3 (15)
Any increase between pairs of serum samples† 726 180 38 (21.1) 37 9 (24.3) 32 4 (12.5)

*Percentage of the participants who demonstrated a ≥4-fold increase in titer who also self-reported an influenza-like illness (ILI) during follow–up.
†From enrollment to 12 mo, 12 to 24 mo, or enrollment to 24 mo, among participants who permitted serum sample collections at least 2 times during the study.

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Page updated: July 06, 2010
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