Smallpox was also common during the Industrial Revolution. Smallpox was the deadliest disease known to mankind during that time period. Smallpox is less commonly known as Variola. The first vaccine was developed by Edward Jenner in 1748, but was not tested until 1805. Smallpox is caused by the very contagious virus Variola Major. Smallpox spread through the the mills because the mill owners disregarded the developed vaccine.