One of the biggest jumps in life expectancy coincided with the introduction of sewers, which greatly reduced the spread of disease.

Life expectancy increased dramatically in the 20th century, especially in developed nations. These gains were due largely to the eradication and control of numerous infectious diseases.

The major exception to this general pattern of improvement has been in those countries worst hit by AIDS, principally Sub-Saharan Africa, which have seen significant falls in life expectancy due to the disease in recent years.