Epidemiology has several objectives depending on the subject being studied and the hypothesis being tested :
To identify the etiology or cause of a disease and the associated risk factors (factors that increase the risk for this disease)
To determine/quantify the spread of a disease in a community
To study the natural history of a disease and its prognosis
To evaluate new measures to prevent and treat diseases, and new means to provide access to and dispense healthcare
To find strong arguments to develop healthcare policies and to make decisions that are in line with environmental problems