Dale Grosskurth, the health department's environmental health and safety director, said dogs are especially vulnerable to contaminates.
"Part of the reason dogs can be affected more readily is because they tend to be smaller and they lick their skin dry, or lick their fur," Grosskurth said. "And they can ingest an organism that way."
He said you should dry yourself and your dogs after getting out of the water. Showering helps to wash away toxins or microorganisms that can cause illness.
Diane Stanek, who works at the Lake DuBay Shores Campground, said she thinks Lake DuBay stays pretty clean since the Wisconsin River flows through.
"Most of the time, the waters are safe," Stanek said, "Especially for dogs. They drink lake water. They drink all kinds of water."
Grosskurth said the health department doesn't regularly tests lakes or rivers. The tests take a few days to complete, and by then, sometimes the water conditions have changed.
Grosskurth said he doesn't think E. coli is to blame for the dogs' deaths this week since it usually takes longer for symptoms to appear.
According to Grosskuth, June through September are prime times for blue-green algae to produce a toxic chemical. He said if you can see two-feet into the water, that's a good indication it's okay to get in.