The outbreak mentioned was caused by Cryptosporidia, a microscopic parasite that infected thousands of people. Some died, especially those who had weakened immune systems. This is not the first time something like this has happened. Some researchers state that the waste material produced by flukes is extremely carcinogenic and contributes to the formation of cancer. The waste material from just one tapeworm can make someone ill.
Microscopic parasites can cause arthritis-like symptoms.
It is impossible to avoid all situations that could lead to parasitic infection. Drink clean, pure water. Distilled water is best to drink. However, there are many purification systems that produce clean water. Reverse osmosis, carbon block and other types of systems can ensure that the water you drink is free from possible contamination.