Smallpox is a contagious infection caused by the variola virus. Smallpox can be deadly. The best thing you can do to protect yourself from smallpox is to get vaccinated. If you have symptoms of smallpox -- such as severe illness with a high fever, then a body rash -- seek medical care. Follow the links below to find WebMD's comprehensive coverage about how smallpox is contracted, what it looks like, how to treat it, and much more.