Many of the diseases that cause epidemics in the world today are thought to be triggered by changes of man’s interactions with the environment. Three such cases are recent outbreaks of cholera, the plague, and Lyme disease.

In 1991, cholera was detected for the first time in one hundred years in Peru. Cholera is an acute intestinal infection caused by bacteria. It is spread by contaminated water and food (usually raw fish), and through contact with contaminated human feces. It is often associated with algal blooms (plankton), which are influenced by the temperature of the water. The outbreak in Peru was thought to be a result of El Niño, which increases the temperature of the water.

When cholera occurs in an unprepared community, case-fatality rates may be as high as 50% -- usually because there are no facilities for treatment, or because treatment is given too late. In contrast, a well-organized response in a country with a well established diarrheal disease control program can limit the case-fatality rate to less than 1%. Treatment

Lyme disease is again caused by a bacterial infection. Lyme disease is spread when immature ticks become infected by feeding on small rodents. In later stages, these ticks then transmit the Lyme disease bacterium to humans and other mammals during the feeding process.

The outbreak in India was triggered by an earthquake over 300 Km away. The earthquake disturbed the rodent populations in neighboring forests and entered into the city of Surat. The earthquake also cased the city to be flooded. The combination of stagnant water and incoming rodents provided a perfect scenario for a plague outbreak.

In northeastern United States, Lyme disease is such a problem because people are encroaching on wooded areas to build homes. Living in wooded areas increases the exposure one has to ticks. Lyme disease is curable if detected early enough with a heavy regimen of antibiotics. However, it is often hard to detect when someone has been bitten by an infected tick because the immature ticks are very small and hard to see.

Each of these examples show how human interactions with the en

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