Officials in Winnebago County are warning people about blue-green algae which are blooming on area lakes. Nutrient run-off is combining with the heat and recent rains to expand the problem. Contact can cause headaches, vomiting, and a rash, so health officials are telling people to avoid contact with it. Although occurrences are rare, it can lead to liver failure. Reports have been received of blue-green algae on Lake Winnebago. Experts say it can contain multiple colors and it might look like paint floating on the water.