Herpes simplex viruses. Coloured transmission electron micrograph (TEM) of three herpes simplex viruses. There is a grey envelope surrounding the main body (capsid, rounded stippled purple/white) of two of these viruses. The capsid has an icosahedral (twenty-sided) structure made up of protein. Inside the capsid is deoxyribonucleic acid (DNA), genetic material necessary for the replication of the virus. The herpes simplex virus attacks humans causing cold sores of the mouth, lips and face. While another form of the virus causes genital herpes, spread as a sexually transmitted disease. Magnification: unknown.