Clinical medicineis about understanding at the individual level-history, examination, investigation, diagnosis, treatment, long term follow up and care.

A patient presenting with Angina needs multiple different interventions-he may requires angioplasty, help in altering eating and smoking patterns, attention to life style stresses, weight control and exercise and long term aspirin therapy.

Public Health medicine is about the understanding of communities-their anthropology, sociology, examining their demography and vital statistics, investigating problems and trying to draw effective conclusions around which policy can be made.

E.g. Food rationing in Britain in World War 2.

There was a food shortage,it was imperative to share the food as fairly as possible across the population, to ensure at least adequate calories, protein and vitamins, to provide extra nutrition for pregnant and lactating women and for young children. The nutritionists did their calculations, the demographers their calculations, the government enforced and the people grumbled but accepted the fairness of it and were united in a patriotic struggle.

Public Health will often be about influencing policy decisions and often it will fall to Public Health to implement policy and manage change. Change is about People Change-classically increasing knowledge,.challenging attitude constructively and delivering behavioural change.