Why don't people get sick from swimming in lakes and rivers when they probably ingest plenty of contaminated water?
Submitted by - K.D., Santa Barbara, CA
You're right. There is a risk. People do get sick from swimming in lakes and rivers when they swallow too much water. You have to ingest a certain number of germs or parasites to get sick, the specific number depending on the specific bug. Swimmers do not usually swallow enough water to make them sick. The advice to filter or purify your water is based on the accumulation of germs over time. We are swallowing all the water from the bottle, and spitting out most of the river water. If the number of germs we swallow remains small (and we all swallow a few), most of the time they are destroyed by our body's immune system before they make us ill. So, try to keep as much water as possible out of your mouth when you're swimming in a lake or river–and spit out the water that does get in.