As described in other chapters, public health has evolved from integrating sanitation and hygiene, to including social medicine, community medicine and preventive medicine. If public health is regarded as a discipline that views and tackles issues of disease, and health and health care at the population or societal level, with the aim of fi nding ways of continually improving the health of the population, epidemiology provides the theories and methods for conducting scientifi c research in human populations in public health.