Epidemiology is primarily concerned with the:
Epidemiology: 
Epidemiology is defined as the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems. - John M. Last
Soben Peter 
Essentials of preventive and community dentistry 
4th edition
Identification of the agent causing disease in the host
Occurrence and distribution of disease in the population
Predisposing factors to disease
Relationship between organisms and their environment