There are two clinical forms of the smallpox virus, variola major and variola minor. Variola major causes severe disease by producing characteristic large pustules, or pocks, in the skin, kidneys, lungs, intestines and other organs such as the brain. A rare hemorrhagic form of smallpox causes blistering and bleeding inside the body, in the stomach and intestines and bleed-out occurs similar to what is seen with Ebola virus. The skin appears to shrivel and blacken, hence the name blackpox.
