Swine Influenza Virus Antibodies in Humans, Western Europe, 2009
Figure. Geometric mean titers (>10) of antibodies against pandemic (H1N1) 2009 virus, seasonal influenza (H1N1) virus, and swine influenza virus of swine workers (A, B, C) and controls (D). Each symbol represents titer of 1 person; only persons with positive results (>10) for at least 1 of the 2 viruses of the panel are shown. Trend lines are shown; R2 values were R2>0.01 for panels A, B, and D and R2 = 0.5 for panel C.