B.M.
OOOOHHHHHH have I so been there. Both of my children have been bitten repeatedly at daycare. I am told that it is because my children are social and non-aggressive, so they are viewed as good targets by the biters, who rightly assume that my kids generally won't fight back. It is *incredibly* frustrating as a parent and I almost pulled my daughter out of the daycare because I did not feel like they were responding to my needs.
First step is to make sure your daycare/teachers are paying attention. You say you are comfortable with that, so good.
If possible, ask that your child be separated from the biter. If there is another class your child can go to (in the same daycare), that may be worth looking into.
Next step is to teach your child to say, loudly and emphatically, "NO BITE!" You want the teachers to reinforce this as well by telling the biter not to do that, clearly and consistently. Work with the teachers to be sure they are encouraging your child to say "NO BITE!" every time. Eventually the other kids pick up on it too and it becomes a form of peer pressure against the biter.
Those are the condoned methods in a daycare situation. Now I will tell you, with my son we are encouraging him to stand up for himself as well, and if that turns out that the biter gets punched in the nose, well, I'm willing to take that incident report. This is not necessarily the method you should try, I'm just saying that's what we are doing after seeing both of our kids go through this. [However I will note that my son apparently interprets this as PINCH someone in the nose, which is sort of funny. And hey, if it works..... We tried to get my daughter to do it as well but she never took to it. Probably a good thing for the biters.]
You should also know that there are 2 stages where they go through biting. You are probably in the first round. It will ease off and then there will be a resurge of it in about 8 months to a year. Be prepared for that.
I was also afraid that my kids would learn to bite but they never did. It does not seem to work that way; biters seem to be prone to it and non-biters aren't. If they aren't already prone to be a biter, it doesn't seem to trigger it.
Also it does not seem to influence the bitten child to the point of fear, although we do have one boy in my son's daycare class he refers to (because we do) as No-Bite Jace. He still plays with Jace, though.
Hang in there, I know it's tough. It will get better and it will go away.