Pseudorabies is a viral disease that is endemic to swine in most parts of the world and also infects many other domestic and wild animals (in cattle it is known as "mad itch"). For the virus to infect a cell, a series of proteins must interact to fuse the virus's envelope to the membrane of the cell so that the viral payload can be delivered to the cell's interior. In this image, one of these proteins (glycoprotein B, which appears in red) coats the surface of infected pig kidney cells.