C.A.
Well, I am not 100% certain that this is the same thing, BUT, my daughter had one of the coxsackie viruses which is the family of viruses that foot and mouth comes from. The particular type she had is the one where there were blisters on the back of her throat so she did not want to eat or drink. She was 18 months old at the time as well and I think we either got this at daycare or from an unrelated trip to the Dr. Like the other commenter below, I think this was the herpangina form. Looks to me like this is VERY common!
Also like the other commenter, our Dr. suggested 1/4 of a teaspoon of the plain children's benadryl to numb the blisters in her throat, followed by 1/4 of a teaspoon of mylanta to create a coating over the benadryl. That is the most awesome trick ever, probably for any sore throat if you know that's what is going on with your child. Immediately after we did that, my daughter wolfed down a peanut butter sandwich and two sippies full of water. I only had to do that for one evening and then again in the morning and after that she was fine. We also gave tylenol alternating with motrin as needed when the fever started to look too high.
For preventive measures, we are hand washers like you guys. That's the best way to prevent these things but viruses are tough to avoid. Second, I give my daughter 250 mg of vitamin C every day. When I think she's getting sick, I add doses of a kid's formula of Echinacea/GoldenRoot that they sell at Sprouts. We still get sick but not nearly as often or as seriously anymore (HOORAY).
Hope this helps! Good luck and hope your baby gets to feeling better soon!