Based on the results of restriction endonuclease analysis, isolates of BoHV-1 can be subdivided into three subtypes. BoHV-1 type 1 (BoHV-1.1) isolates are typically associated with respiratory disease and abortion and are sometimes referred to as being IBR virus-like. A second group of viruses, referred to as BoHV-1.2 are typically associated with venereal infection and are referred to as being IPV-like. This grouping can be further subdivided into BoHV-1.2a and −1.2b, being clinically distinguished by the association of the former with abortions, although these distinctions between subtypes are not absolute.