A Porcine Epidemic Diarrhea Virus Outbreak in One Geographic Region of the United States: Descriptive Epidemiology and Investigation of the Possibility of Airborne Virus Spread

Beam, Andrea; Goede, Dane; Fox, Andrew; McCool, Mary Jane; Wall, Goldlin; Haley, Charles; Morrison, Robert

Data were then imported into ArcGIS for analysis. A hotspot analysis (Getis-Ord Gi à ) was performed to identify statistically significant geographic clusters of PEDv cases. The ArcGIS "Optimized Hotspot" tool was used for this analysis. The tool evaluates the characteristics of the outbreak data by running a Global Moran's I test to identify distances in which clustering appears within the dataset. A neighborhood search radius of 11.5 miles was selected for this cluster analysis based on the results of the Global Moran's I statistic. A hotspot surface was then generated using resulting z-scores from the analysis as input to the inverse distance weighting interpolation tool. The resulting surface shows geographic areas with significant clusters of positive sites in red and areas without significant clustering of positive sites in blue. A directional ellipse tool in ArcGIS was also used to describe the overall directional orientation of PEDv positives from week to week. This tool uses the standard deviation of the x and y coordinates from the mean center (of weekly incident cases) to define the axes of the ellipse. The resulting weekly ellipses show the distribution and orientation of PEDv cases on a weekly scale.