Human respiratory syncytial virus (RSV) is a member of the Paramyxoviridae family, subfamily Pneumovirinae, that causes common respiratory tract infections such as measles and mumps. Its genome consists of single stranded, negative sense RNA that encodes three envelope glycoproteins, a small hydrophobic (SH) protein of unknown function, a major glycoprotein (G) known as the attachment protein, and a fusion (F) protein. Its name comes from the fact that F proteins on the surface of the virus cause the membranes on nearby cells to merge, forming syncytia. While RSV typically produces mild symptoms in adults, it is one of the leading causes of lower respiratory tract infections and hospital visits during infancy and childhood.