DNA viruses that infect humans have a double-stranded DNA genome encased in a protective shell, called acapsid, which may in turn be enclosed in an envelope. These envelopes give viruses certain advantages, like ease of infection. On the flipside, an envelope makes a virus more sensitive to environmental destruction.In any case, once the virus gains entry into the human body, it must touchdown on the surface of a cell it's going to infect. I picture it almost like a moon landing of sorts. Viruses have little adhesion molecules, like legs on a lunar module, that will stick to the surface of a cell, or the moon's crust. Once the virus, our lunar module, touches down on the surface of its cell, it will then trick the cell into allowing it entry into the cytoplasm, or the mantle of the moon. After drilling down below the surface of the moon, through the mantle, or cytoplasm, the DNA viral genome enters into the core of the moon, or the nucleus of the cell. This is where it will do its dirty work.