The river water is tested in line with BTF guidance. If the river is not safe to swim in, the race will become a duathlon (i.e. run/bike/run).  There will always be a risk of illness when swimming in open water. To minimise the risk competitors should wash hands before eating or drinking anything (including after handling your wetsuit), aim to swim away from the edges where the flow is greater and water quality better, ensure any wounds are covered with a waterproof dressing and try to avoid drinking any river water.