| New Technologies |
The evolution of new pathogens is not just a function of human-pathogen or human-human interactions. Sometimes people also unwittingly provide new environments where disease-causing organisms thrive. In the 1970s, for example, air-conditioning systems became widely available. A bacterium normally found in fresh water lakes, Legionella pneumophila, moved into the systems, gaining access to susceptible humans. The result was a previously unreported respiratory infection.