So far this year, blue-green algae has been reported in 12 lakes in the Sudbury area.
A manager with the Sudbury and District Health Unit, Burgess Hawkins, said that number is higher than average. In a typical year, between four and six cases of blue-green algae are reported.
Hawkins said it's difficult for health officials to give a reason for the increase.
Dr. Charles Ramcharam, a biology professor at Laurentian University, said the increase may be due to two reasons: more people may be reporting blue-green algae blooms due to greater awareness and the fact that "it was a pretty warm summer."
"From my own research on Ramsay Lake with my student, it looks like the warmth was a signficant factor in increasing the potential for a blue-green bloom," he said.
Ramcharam says once blue-green algae blooms are present on a lake, it can take up to six weeks for them to break down.
Hawkins noted that blue-green algae blooms are typically prominent between June and October.
He added people who live on a lake that has tested positive for blue-green algae should seek an alternative source of water instead of lake water.