When someone becomes infected, they do not immediately feel sick; it takes about 10 to 12 days for symptoms to start. However, inside the person's body, the smallpox virus is multiplying. This period between smallpox transmission and the beginning of smallpox symptoms is called the "smallpox incubation period." During the smallpox incubation period, a person is not contagious. However, once symptoms of smallpox begin, the infected person becomes contagious. The person becomes most contagious with the onset of the smallpox rash. At this stage, the infected person is usually very sick and not able to move around in the community. Some risk of smallpox transmission lasts until all scabs have fallen off.