Performing a Google search for medical information is a crap shoot. It can lead you somewhere filled with quality content, or it can send you down a trail of wildly inaccurate speculation and conjecture (which isn't all that different from performing an Internet search for anything else, really). But now when you turn to Google for questions about certain health conditions, it will dish out relevant information at the top of the search straight from the Knowledge Graph.
So when you perform a search for the likes of frostbite or the measles, Google will touch on information such as symptoms, treatments, whether something is contagious, and which age ranges are the most susceptible. Some searches will come with illustrations to provide further clarification.
Google worked with a team of doctors to compile the information, then had it double-checked by some of its own doctors and others at the Mayo Clinic. The data should be reliable, but don't count on it as medical advice. You should still consult healthcare professionals for serious issues.
Nevertheless, you can still use this information as a more trust-worthy starting off point than some unfamiliar URL. The feature will roll out over the next few days, and it's only available in US English for the time being, but Google hopes to extend it out to other languages as soon as it can.
- Google blog