Volume 19, Number 6—June 2013
Research
Active Surveillance for Influenza A Virus among Swine, Midwestern United States, 2009–2011
Figure 1
![Swine influenza virus group status for 32 pig farms participating in an active surveillance project, midwestern United States, June 2009–December 2011. Each horizontal line represents a farm, each dot represents a sampling event, and colors indicate virus status of the group.](/eid/images/12-1637-F1.jpg)
Figure 1. . Swine influenza virus group status for 32 pig farms participating in an active surveillance project, midwestern United States, June 2009–December 2011. Each horizontal line represents a farm, each dot represents a sampling event, and colors indicate virus status of the group.
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