I actually checked a similar ‘symptom’ keyword for a potential client last night and noticed this change today. Here’s a close up of the change:
Notice the result just under the paid listings: the NIH or National Institutes of Health. If the .gov didn’t give it away, this is an institution of the US government. I’m not sure how NIH got in above the one box type refinements Google’s had on SERPs for a while now–conspiracy theories welcome.