Table 1.

The Three Epidemiological Transitions.

Transition	Paleolithic Baseline	First Transition	Second Transition	Third Transition
Time Period	Pre-Neolithic Cultures; More recent hunter-gatherer cultures with little outside contact	Neolithic cultures-Early Modern Times in Western Europe and United States; Still characterizes many low-income countries	Early Modern times to 20th century in Western Europe, United States; Occurred more recently in some other high-income countries and is in progress in lower income countries	End of the 20th century to the present, global
Characteristics	Pre-agricultural Low mortality and fertility rates Small population size Varied diet	Agricultural High mortality and fertility rates Large population size Diet heavily reliant on crops	Agricultural Low mortality and initially high then low fertility rates Large population size Increased life expectancy Varied diet, overnutrition common Discovery of antimicrobials and vaccines, improved hygiene	Agricultural Large population size Declining life expectancy? Failure of antimicrobials Rapid spread of novel infections Age of onset of chronic diseases delayed in high-income countries
Common causes of morbidity and mortality	Infections such as tapeworms, body lice, pinworms, typhoid, staph, and possibly yaws	Infections such as malaria, smallpox, measles, tuberculosis Nutritional deficiencies	Degenerative diseases such as heart failure, stroke, diabetes, cancer Allergies, asthma, autoimmune diseases Sexually transmitted infections such as HSV-2, gonorrhea, HIV	Those diseases present in the 2nd transition Antibiotic resistant forms of tuberculosis, strep, staph, etc.