Species Affected
Smallpox only affects humans. Transmission of the virus occurs through inhalation of airborne Variola virus from an infected person. Smallpox often results in death. Smallpox attacks all parts of the body, and spreads mainly through the circulatory system. It destroys the immune system by killing macrophages. It also attacks blood vessels in the skin. The circulatory system carries the virus to the internal organs. The virus reproduces in many of the organs, including the spleen, lungs, and liver.