Class I viruses with double-stranded DNA genome that codes for more than 30 polypeptides. They are the largest viruses and their shell is complex, consisting of many layers, and includes lipids and enzymes, amongst which is a DNA-dependent RNA polymerase. Uniquely among the DNA viruses they multiply in the cytoplasm of the cell, establishing what is virtually a second nucleus. The most important poxviruses are vaccinia, variola (smallpox), and myxoma virus.
Dictionary of molecular biology. 2004.