Comparison of PRRS effect on performance in US and Denmark

It is uncommon for two pieces of valuable information to come out at more or less at the same time, so one is bound to make a comparison. The data has not been collected in the same way but appears to be robust. So what are the differences between US PRRS and EU PRRS? A paper by Kristensen and Vinther (2013) from Denmark, reviewed the effects on performance of porcine reproductive and respiratory syndrome (PRRS) virus on breeder and finisher herds by comparing herds recorded as PRRS negative and