Smallpox viruses. Coloured transmission electron micrograph (TEM) of a section through Variola viruses, the cause of smallpox. Variola belongs to the orthopoxvirus group of viruses. The virus has a protein coat (capsid, green) surrounding its DNA (deoxyribonucleic acid, red) genetic material. Smallpox was eradicated from the world by a global vaccination in the 1970s. Isolated cultures of Variola viruses are still kept in laboratories for research purposes. The disease causes high fever and skin spots that quickly develop into scarring pustules. The virus is transmitted by coughed droplets or the pus from pustules of an infected person. Magnification: x120,000 at 6x7cm size.