We’ve all done it: You plug your aches and pains into WebMD’s Symptom Checker, see that it could be either “cancer” or “seasonal allergies,” and promptly close out the window and decide to ignore ...

For a few days around Christmas, Holly Jespersen, a 50-year-old living in New York, did not feel great. It felt like a cold was coming on, but she wasn’t sure if she should go to the doctor or not.