Smallpox virus. Illustration of a section through a smallpox (variola) virus. The core (red) contains the particle's DNA genetic material. The core is overlaid with several layers of a membrane derived from its host cell. The core has a biconcave shape. The depressions in its upper and lower surface contain lateral bodies (purple), the function of which is unknown. Smallpox is a disease that causes fever and often death. It was eradicated after a worldwide effort in the 1970s, but strains exist in research laboratories. For an artwork of the outside of a smallpox virus, see image C056/3333.