The Madison-Dane County Health Department says at least one person appears to have been sickened by blue-green algae while swimming in Lake Mendota.

Eighteen-year-old Brianne Schuetz of Madison says she swam in the lake near the University of Wisconsin's Memorial Union last week. She says she has been suffering from joint pain, a headache, rash, upset stomach and fatigue since then.

The health department's environmental technical services supervisor, Kirsti Sorsa, says Schuetz is the fourth person in the area this year who may have been sickened by algae.

Blue-green algae are common in Wisconsin waters. The algae often look like scum on the surface and have an unpleasant odor.

Sorsa says the possibility of algae in Lake Mendota could be a serious health situation.