What are the symptoms of smallpox?
The initial symptoms of smallpox, 7 to 17 days after exposure, include the acute onset of fever, chills, headache, nausea, vomiting and severe muscle aches. During this time, the infected person feels fine and is not contagious. The symptoms of smallpox begin with high fever, head and body aches, and sometimes vomiting. A rash follows that spreads and progresses to raised bumps that crust, scab, and fall off after about three weeks, leaving a pitted scar. This stage generally lasts for two to four days and can be accompanied by flushing of the skin. By the fourth day of illness, the fever drops and the
characteristic smallpox rash appears. The rash starts out flat or slightly thickened spots (known as macules) and quickly progresses to raised spots (known as papules). These papules continue to enlarge and become filled with a clear fluid, then referred to as vesicles. The fluid in the vesicles gradually changes from clear to pus-like, and the lesions are then referred to as pustules. During the pustule stage, a fever is common and the pustules start to form into scabs. Over time, the dried scab material falls off of the skin. This entire process takes three to four weeks, and the areas affected by the rash can be permanently scarred.
There are two types of smallpox: variola major and variola minor. Variola major is the more severe form and has a 30-50% fatality rate among those who are unvaccinated (3% in vaccinated persons). Variola minor has a 1-2% fatality rate in unvaccinated individuals. There are two rare and more serious forms of smallpox. In the most severe, known as purpura variolosa or hemorrhagic-type smallpox, the initial stage of the illness (before the rash appears) is accompanied by a dark, purplish, blotchy flushing of the skin. People who developed purpura variolosa usually have a severe loss of blood into the skin and internal organs (hemorrhage), and die before the typical smallpox rash appears. About 3% of the persons with variola major develop purpura variolosa.
Another rare and deadly form of smallpox is referred to as flat-type smallpox affects about 5% of the persons with variola major. Persons with this form of the disease have lesions that develop more slowly, never raised above the surface of the skin, and feel soft to the touch. If people with flat smallpox survive, they rarely experience severe scarring. Both purpura variolosa and flat smallpox are virtually never seen in persons infected with variola minor.