Doesn't really matter what our thoughts are, we're not doctors - go on an NHS or medical site with some real experts on. But my views for what they are worth Punting is no riskier than any other sex unless you only make love to Nuns. So like any sex take precautions and get tested regularly.
But if you're worried about any sexually transmitted disease then don't have sex! And don't drive or go out, don't drink or smoke, don't eat unhealthy food, don't meet anyone else. You'll live forever, but you'll be so bored you won't want to!