» For the leaf bug, see Miridae. A capsid is the protein shell of a virus. It consists of several oligomeric subunits made of protein. The capsid encloses the genetic material of the virus. Capsids are broadly classified according to their structure. The majority of viruses have capsids with either helical or icosahedral structure. Some viruses, such as bacteriophages, have developed more complicated structures. The icosahedral shape, which has 20 equilateral triangular faces, approximates a sp… (More on Capsid)