Porcine reproductive and respiratory syndrome (PRRS) virus remains a very important disease of swine in the United States. At the University of Minnesota Veterinary Diagnostic Laboratory, hundreds of samples are routinely tested for this virus by polymerase chain reaction (PCR) every month. This test can differentiate between the two main types of PRRS virus: the European type and the North American type. Both types have been described in the United States.
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