We had an infection control specialist come speak to us in my EMT class tonight. This guy has taken some big certification test and works closely with the CDC. During his four hour talk, he had some great stories and explanations.
Why hamburger meat must be fully cooked: I always wondered why restaurants only serve hamburgers fully cooked. I know my mom and several others prefer them a little more rare. However, all restaurants will serve a steak rare. The specialist informed us that the bacteria is found in the exposed part of the meat (the outside). Even a rare steak is cooked on the outside, if not at all on the inside. The problem with hamburger meat is that it is all mixed together so it all must be thoroughly cooked.
To ruin sweat tea for all the true Southerners: The process of making sweat tea, especially when the tea is hot and sugar is added, creates an incubator for bacteria. Most people let the tea cool naturally rather than running it over ice to speed it along. The bacteria thrives in the warm environment with sugar. He also said the bad taste you get when tea has gone bad is when the bacteria has grown enough that you taste the bacteria over the tea and sugar. (This particular topic came up during a Hepatitis A discussion.)