Bourbon virus. Negative stained transmission electron micrograph (TEM) of a filamentous Bourbon virus (Thogotovirus) particles (virions). Bourbon virus belongs to a group of viruses called thogotoviruses, which are found all over the world, a few of which can cause illness in humans. It is not yet fully known how people become infected with bourbon virus. However, based on what is known about similar viruses, it is likely that it is spread through tick, or other insect, bites.