Structure
Smallpox is caused by the Variola virus. This virus is a DNA virus, but replicates in the cytoplasm instead of the nucleus like other DNA viruses. Most viruses have a capsid, an envelope, and a core. The capsid is the protein shell that encloses the viral genome. The capsid can be one of several shapes, depending on the virus. It may be helical, polyhelical, or complex. Capsids are made out of many protein subunits called capsomeres. Envelopes are membranes cloaking the capsid that help viruses enter host cells. They are typically derived from portions of the host cell membranes but also contain proteins and glycoproteins of viral origin. The core is a protein coat that contains the virus' genetic material. Virus' have either DNA or RNA, but not both.
The variola virus structure is DNA double stranded and enveloped. An envelope made of a host cell membrane surrounds the virus. The envelope has surface tubules attached to the outside that help it bind to the host cell. The dumbbell shape structure is the viral core, which stores the DNA.