Dr. Colm Henry:

The training and expertise of public health departments is focused on outbreak management in pandemic situations such as the current one. They tend not only to break the chains of transmission by identifying index cases and their close contacts but they also work backwards, looking for common threads leading to a common source. Some of the outbreaks and common sources identified, notably in examples provided at press conferences, have been of people meeting at sports facilities, leading to a number of people testing positive for the virus. It is in the nature of public health at the outbreak and investigation stages to look backwards.