NOVEL ENVIRONMENTAL FACTORS
Bubonic plague, the black death, had long festered in Asia, but became epidemic only when Mongol invaders brought it to unexposed populations in Europe who lived with large populations of flea-infested rats. While we like to imagine that such events are in the past, AIDS continues to spread alarmingly, and the causes of other sudden outbreaks of infec- tion are unknown. The Ebola virus ravaged parts of Africa in the 1980s, killing half of those who became ill, including most of the doc- tors and nurses who cared for the patients. It stopped as suddenly as it started, for reasons that remain unclear.
Some infectious diseases stem directly from modern technology. Legionnaires’ disease arose from an organism that was able to grow and be dispersed from the water in a hotel air-conditioning system. Toxic shock syndrome arose when a new superabsorbent tampon material allowed enough surface area and oxygen for the growth of unusually large concentrations of toxic staphylococcal bacteria. Lyme disease became a problem only when deer populations multiplied adjacent to new suburbs. Influenza has become a major threat since mass worldwide transportation began spreading new strains that con- tain new genes. It is often called the Asian flu because new strains so often originate on Asian farms, where people, ducks, and pigs (some strains are called swine flu) live in such close proximity that genes from one influenza strain can easily be passed from one to another.
