Panfish, I spoke with DNR about this issue yesterday because my son and a bunch of his friends wanted to go skiing, The officer was more than helpful. They test the lake daily and have had no other positive test since for Ecoli. He told me that in his opinion it was ok for my son to have fun on the lake, He also told me that this happen more than people realize he said after a heavy rain goose poo gets washed in to the lake and it will 9 times out of 10 cause a positive test.
anyway just my 2 cents.