Epidemiological Transition

The epidemiological transition is the long-term change in the diseases that affect a population and the causes of its deaths. It describes a shift from a pattern dominated by infectious diseases, nutritional deficiencies and maternal and childhood conditions towards one in which non-communicable diseases account for a larger share of illness and mortality.

How disease and mortality patterns change

As deaths from infections and other preventable causes decline, more people survive into adulthood and older age. Chronic illnesses consequently become more prominent, although changing lifestyles and exposures also influence this shift.

• An earlier pattern commonly involves high mortality from communicable diseases, undernutrition and conditions associated with pregnancy, childbirth and early childhood.
• A later pattern gives greater prominence to cardiovascular diseases, cancers, diabetes and chronic respiratory diseases, many of which require prolonged care.
• The transition concerns the composition of disease and death: a declining percentage of deaths from infections does not necessarily mean that their absolute number falls.

What drives the transition

The transition reflects interacting changes in living conditions, public health, medical care, population structure and behaviour. It is closely related to, but distinct from, the demographic transition, which concerns changes in birth and death rates.

• Safer water, sanitation, better nutrition, vaccination and effective treatment reduce mortality from many infectious diseases.
• Longer survival and population ageing increase the importance of chronic diseases.
• Tobacco use, unhealthy diets, insufficient physical activity and harmful alcohol use contribute to non-communicable disease risks; urbanisation can alter these exposures.

Why the transition is uneven

The transition is not a uniform or irreversible sequence. Different diseases can coexist, and progress varies across regions and socioeconomic groups.

• A double burden of disease arises when substantial infectious, maternal and nutritional problems coexist with a growing burden of non-communicable diseases.
• India illustrates this overlap, with considerable differences in the stage of transition across states.
• Epidemics and emerging or re-emerging infections can disrupt progress even where chronic diseases dominate mortality.

Implications for health services

Health systems must expand prevention and long-term care for chronic illness without weakening infection control, nutrition programmes or maternal and child health services.

• Strong primary health care can combine vaccination and communicable-disease control with risk reduction, screening, continuing treatment and referral.
• Planning must address disability and quality of life as well as survival, because longer life does not automatically mean healthier life.