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Genetic analysis of porcine reproductive and respiratory syndrome virus (PRRSV) field strains is necessary to control the disease.We analyzed the nucleotide sequence variation of North American genotype (type 2) PRRSV strains in Japan and compared them with those of PRRSVs from other countries.In addition,the genome of European genotype (type 1) PRRSV isolated for the first time in Japan in 2008 was analyzed.The ORF5 genes of 57 type 2 PRRSVs isolated from lung samples of pigs with respiratory signs in the various areas of Japan in 2009-2011,were sequenced.