The responses of the Public Health Departments in Europe and in the United States represented the ideas prevalent in society and in the scientific community. While most of the measures were solidly grounded in the current scientific concepts, they could also be traced back to Medieval and even Classical times of plague and pestilence. The idea of contagion prompting quarantines and isolation dates back to the Justinian Plague. However, epidemiological work by Snow and others in the 19th century did further these notions of contagion and understanding of transmission. Public Health Departments grew out of these advances and the belief in the ability of man to control nature. Sanitation, vaccination programs and other public hygiene efforts in the late 19th century enabled public health officials to gain power and authority. However, the Influenza Pandemic of 1918-19 challenged the public health agencies.
