LABELLE, FLA.—Health officials in Florida say a 12-year-old boy is fighting a rare and deadly infection that is attacking his brain.

Family members told media outlets that Zachary Reyna of Southwest Florida was infected with Naegleria fowleri, a microscopic single-celled living amoeba that is commonly found in freshwater lakes, ponds and rivers. State health officials say it can cause a rare brain infection called primary amebic meningoencephalitis (PAM) that destroys brain tissue and is usually fatal.

Victims typically are exposed to the bug while swimming or doing water sports in warm ponds, lakes and rivers during the hot summer months, mostly in the South.

Family members said the boy was infected while knee boarding with friends in a ditch near his family’s house on Aug. 3. He is being treated in the intensive care unit at Miami Children’s Hospital.