Diagram showing sharp birth rate and death rate decreases between Time 1 and Time 4, the congruent increase in population caused by delayed birth rate decreases, and the subsequent re-leveling of population growth by Time 5. In demography and medical geography,<unk>  is a theory which "describes changing population patterns in terms of fertility, life expectancy, mortality, and leading causes of death." For example, a phase of development marked by a sudden increase in population growth rates brought by improved food security and innovations in public health and medicine, can be followed by a re-leveling of population growth due to subsequent declines in fertility rates. Such a<unk>  can account for the replacement of infectious diseases by chronic diseases over time due to increased life span as a result of improved health care and disease prevention. This theory was originally posited by Abdel Omran in 1971.
Epidemiological transition
Spillover 
Therapeutic relationship
Risk factor
Recrudescence
Benefit period
Incubation period
Adherence 