It's microscopic, unassuming and incredibly deadly.The Southern Nevada Health District says a boy has been killed by a brain-eating parasite following exposure at the Kingman Aash area on the Arizona side of Lake Mead.Dr. Daliah Wachs, a family physician, says the amoeba enters the body through the nose, enters the brain and wreaks havoc, causing inflammation, seizures, coma and eventually death, with little that can be done to fight back. Officials say the brain-eating amoeba only lives in and is common in warm freshwater environments like Lake Mead.However, infections are incredibly rare because it can only enter the nose. Watch the video above for the full story.