Immunology and Virology Diseases

Variola Virus Evolution

Variola virus, the agent of smallpox, has a severely restricted host range but a devastatingly high mortality rate. Although smallpox has been exterminated by a World Health Organization vaccination program, awareness of the evolutionary processes by which human super-pathogens such as variola virus arise is important. Variola virus tended to attack skin cells, causing the characteristic pimples, or macules, associated with the disease. A rash developed on the skin 24 to 48 hours after lesions on the mucous membranes appeared. Typically the macules first appeared on the forehead, then rapidly spread to the whole face, proximal portions of extremities, the trunk, and lastly to distal portions of extremities.