Smallpox was a dangerous disease caused by the variola major virus. The most common type of smallpox, ordinary, historically has devastated populations with a 30% death rate. The smallpox virus is transmittable through bodily fluids and materials contaminated with infected materials. Generally, face-to-face contact is required for an individual to contract smallpox as a result of an interaction with another human. Unlike some viruses, humans are the only carriers of variola major. This limits the chances of the virus being unknowingly spread through contact with insect or other animal populations. Persons infected with smallpox are infectious to others for about 24 days after their infection time. However, there is a period of time in which individuals are contagious but have only begun to experience minor symptoms such as fever, headaches, body aches, and sometimes vomiting.