The PRRS virus is a serious problem for hog producers but it is often difficult to understand the economic impact of PRRS on a herd. In order to acquire a solid understanding of the impacts of a PRRS outbreak, researchers looked at hog operations in the mid-west United States to gain data. Sites were ranked based on there PRRS infection rates: 0 – consistent production of PRRS negative pigs, 1 – PRRS infected herds with no sign of PRRS in the nursery, and 2 – PRRS positive pigs in the nursery. Pig flows were tracked over seven months, and nursery data and finishing data was collected. Analysis of the data was able to provide a good look at the cost of PRRS, stating that:  Income per pig weaned for status 0 was $42.64, for status 1 $40.46 and for status 2 it was $35.57. Also the PRRS status of each site moved linearly with wean-finish performance.