Choropleth map of proportional morbidity ratios (PMR) of FIV to FeLV infection in the US. Colors on the map depict the range of PMR values for 48 contiguous states and District of Columbia of the US. Red and blue borders indicate high risk areas of FIV and FeLV infection relative to each other. These high risk areas were identified as 'clusters' by spatial scan test using a weighted normal model. Areas with blue borders depict administrative regions where FIV infections are greater than FeLV among cats. Areas with red borders indicate administrative regions where FeLV infections in cats are greater than FIV.