What is smallpox?
Smallpox is a highly infectious disease that is caused by two forms of the variola virus: variola major (the most common and most severe form) and variola minor.
Of the four subtypes of variola major-ordinary, modified, flat and hemorrhagic-the last two are rare but almost always fatal. In general, when people talk about smallpox, they are referring to the most common type, ordinary variola major.
How does it spread?
The smallpox virus is spread through the air when an infected person coughs, sneezes, or just talks. It can also be spread through direct contact with contaminated clothing or bedding. The inhaled virus attaches to the lining of the throat and/or lung and then enters the bloodstream, where it can infect the internal organs and skin.
The infected person usually is not contagious until symptoms appear, specifically after the appearance of the rash, which occurs about two weeks after exposure to the virus.
What are the symptoms of the disease?
Approximately ten days after someone is exposed to the virus they will begin to experience vague symptoms such as high fever, headache, backache, nausea, vomiting, and general malaise.