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History and Prokaryotes

Behavior Changes and Diseases

Bacteria cause a number of diseases. Pathogenic bacteria are often present in the environment but their ability to spread is affected by technological developments and the way we live. Our understanding of how disease works has helped in this process. If we understand how diseases are spread, we can often fix the problem.

Cholera: Breakdowns in Clean Water Systems

Cholera used to be important across the world, including in North America. It is still a big killer in developing countries, but has, for the most part, been eliminated from the developed world by universal access to clean drinking water. As soon as water systems are interrupted, however, cholera can quickly make incursions. This was seen after the 2010 earthquake in Haiti as well as in various ongoing warzones.

Progress, however, continues to be made in both high-tech and lower-tech ways. Check out this cool success story about cholera in Bangladesh.

Lyme Disease: Symptom of Suburbanization

The bacteria that cause Lyme disease lived in deer for a long time. The disease only became a serious issue as the suburban population of humans increased, and natural predators of deer (like wolves) decreased. Humans now live in much closer contact with a larger deer population than they did before. This has resulted in the spread of the bacteria to humans and the high levels of Lyme disease we see today.

Certified Lyme disease killers (below):

Legionnaires’ Disease: A Disease of Climate Control

Legionnaires’ disease is a deadly disease that begins with cold-like symptoms. It is named after its first appearance at an American Legion conference in Philadelphia in 1976. Legionnaires’ disease is caused by a bacterial infection of macrophages, cells involved in our immune systems.

Legionella bacteria enter the body through inhalation of small droplets in liquid (called aerosols) into the lungs. Our exposure to Legionella-infected aerosols has risen with the invention and use of aerosol-generating equipment such as air conditioners and humidifiers.


Each of these diseases follows from shifts in human behavior. Our approach to treating infectious diseases therefore needs to encompass both chemical agents like antibiotics as well as broader societal issues like wolf populations, clean water, and clean air conditioners.

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