The etiologic agent of porcine reproductive and respiratory syndrome is a virus in the group Arteriviridae. The virus is enveloped and ranges in size from 45 to 80 mm. Inactivation is possible after treatment with ether or chloroform; however, the virus is very stable under freezing conditions, retaining its infectivity for 4 months at −70°C (−94°F). As the temperature rises, infectivity is reduced (15–20 minutes at 56°C [132.8°F]).
