Though not often deadly to an adult—or so I have read—the bite of a copperhead snake is something to be concerned about. An old guy once told me that he had been bitten on a finger while a youngster by a copperhead and that finger has been curled and useless all his life. Apparently, the poison went into once of the nerves on the finger.
I had a friend who went through that, but she was only bitten once. It was awful. Took a long time and much medical care to recover.
When my dad was a kid he was bitten on the middle finger tip by a copperhead. It killed the meat on the side of his last digit and he had a half a fingernail and kind of pointed fingertip for the rest of his life.
The cottonmouth bite he got on his foot when he was a kid healed much better.