I mean, if you're going to attempt to kill with a bite, I'd assume they're going for the neck or other particularly vulnerable place. I'd argue commoner bite attacks should have very low chance to hit, but could plausibly be lethal. Most places they get a good bite won't be able to do any damage, except maybe cause a Con save for disease.... I'd say an improvised attack with Disadvantage for 1d6 damage probably works pretty well.