Figure 1. Boxplot of IgG phase I antibodies in two samples obtained from veterinarians (n = 78) and Q fever patients (n = 98) in a three-year time period.

The horizontal dark lines within the boxes represent the median antibody titer, the lower and upper boundaries of the boxes represent the 25^th and 75^th percentiles, and the T-bars represent the 2.5^th and 97.5^th percentiles. Outliers are indicated with dots, extreme outliers (more than three times the height of the box) with asterisks. First serum sample: veterinarians in 2009 or 2010; patients in 2008 or 2009 (twelve months after acute Q fever diagnosis in 2007 or 2008). Follow-up sample: veterinarians in 2013 (three to four years after first sample); patients in 2011 or 2012 (four years after acute Q fever diagnosis in 2007 or 2008). When no end titration available: >1:2,048 categorized as 1:4,096, and >1:4,096 categorized as 1:8,912.