IBR is caused by bovine herpesvirus 1 (BoHV-1).
Family: Herpesviridae
Subfamily: Alphaherpesviridae
There are two subtypes of Bovine Herpesvirus 1:
BoHV-1 is a DNA virus with several structural proteins among which at least 11 transmembrane glycoproteins. Glycoproteins play important roles such as virus-cell interactions and interactions with the immune system. Glycoproteins gB, gD, gH, gK, gL are essential for virus replication, while gC, gG, gI, gE, gM and gN are not essential.

Electromicrograph of a herpesvirus particle.
Marker vaccines that can differentiate infected from vaccinated cattle!