Epidemiological Transition - History

History

In general human history, Omran's first phase occurs when human population sustains cyclic, low-growth, and mostly linear, up-and-down patterns associated with wars, famine, epidemic outbreaks, as well as small golden ages, and localized periods of "prosperity". In early pre-agricultural history, infant mortality rates were high and average life expectancy low. Today, life expectancy in third world countries remains relatively low, as in many Sub-Saharan African nations where it typically doesn't exceed 60 years of age.

The second phase involves advancements in medicine and the devopment of a healthcare system. One treatment breakthrough of note was the discovery of penicillin in the mid 20th century which led to widespread and dramatic declines in death rates from previously serious diseases such as syphilis. Population growth rates surged in the 1950s, 1960s and 1970s, to 1.8% per year and higher, with the world gaining 2 billion people between 1950 and the 1980s alone.

Omran's third phase occurs when human birth rates drastically decline from highly positive replacement numbers to stable replacement rates. In several European nations replacement rates have even become negative. As this transition generally represents the net effect of individual choices on family size (and the ability to implement those choices), it is more complicated. Omran gives three possible factors tending to encourage reduced fertility rates:

1. Biophysiologic factors, associated with reduced infant mortaliity and the expectation of longer life in parents,
2. Socioeconomic factors, associated with childhood survival and the economic perceptions of large family size, and
3. Psychologic or emotional factors, where society as a whole changes its rationale and opinion on family size and parental energies are redirected to qualitative aspects of child-raising.

This transition may also be associated with the sociological adaptations associated with demographic movements to urban areas, and a shift from agriculture and labor based production output to technological and service-sector-based economies.

Regardless, Chronic and degenerative diseases, and accidents and injuries, became more important causes of death. This shift in demographic and disease profiles is currently under way in most developing nations, however every country is unique in its transition speed based on a myriad of geographical and socio-political factors.