1. Bacterial and virus infections: polio smallpox, tuberculosis and related diseases have, to a very major extent, become minor public health concerns 2. An increase in life expectancy resulting from drug therapy has also led to a shift in population demographics toward a more healthy, elderly population 3. Drug regimens for birth control have improved individual life choices and the quality of life• 1. Bacterial and virus infections: polio, smallpox, tuberculosis and related diseases have, to a very major extent, become minor public health concerns. • 2. An increase in life expectancy resulting from drug therapy has also led to a shift in population demographics toward a more healthy, elderly population. • 3. Drug regimens for birth control have improved individual life choices and the quality of life