| genetic variation and phylogenetic analyses of the orf5 gene of acute porcine reproductive and respiratory syndrome virus isolates. | swine herds in the us have experienced recent outbreaks of a severe form of porcine reproductive and respiratory syndrome (designated acute or atypical prrs) characterized by abortion and high mortality in pregnant sows. most of the affected herds had been vaccinated with modified live-vaccines (mlvs) against prrs. to explore the possible mechanism of the emergence of acute prrs, the open reading frame 5 (orf5) gene encoding the major envelope protein (gp5) of acute prrsv isolates was characteri ... | 2001 | 11574173 |