(CBS) — A Minnesota teenager who contracted a brain-eating amoeba while swimming in a lake has died of the rare infection, relatives said.

Hunter Boutain, 14, contracted the disease on Tuesday as he swam in Lake Minnewaska, Minnesota Health Department officials said. He remained in critical condition at the University of Minnesota Medical Center where he died Thursday morning, CBS Minnesota reported.

“Hunter’s condition deteriorated throughout the night and he was declared brain dead this morning,” said his uncle Bryan Boutain, in a statement. “Hunter died surrounded by his family. It is a deeply emotional time for all us. We ask for privacy and prayers as we remember our beloved Hunter.”

The disease is caused by an amoeba often found in freshwater and can enter the brain in water inhaled through the nose.

There have been just 35 confirmed cases of the freshwater amoeba, nationwide, in the past decade. Two of those were in Minnesota.

When confirmed, Boutain’s death would be the third verified death from the amoeba in Minnesota. The other two cases happened in 2010 and 2012.