My sister developed symptoms on Friday just after Thankgiving, and got a positive test back on Saturday. Fortunately, we called off our family gathering for Saturday as a result, so hopefully it was contained to her household only. We were already going to just drop off food at the gathering, anyway, but her positive test made that a formality. I imagine a lot of other struggled with the decision, and many probably elected to go ahead and celebrate with family. I'm sure our #'s will increase over the next few weeks as a result.
In my immediate family (parents and siblings only), we've had two positive cases - my mom and sister (both teachers). The rest of us have done a good job isolating, but both of them had to do some in-person teaching, and surely picked it up that way.