It works both ways: Social media can definitely aggravate our HA, and our HA can make us notice or attend to things we wouldn't otherwise think very much about. Either way it can increase our (false) sense of doom.
Something like this happened to me that's so weird I still can't quite believe it. About a year ago, I was convinced that I had an extremely rare form of blood cancer based on a perfectly normal blood test and my too-active tendency to see patterns. My fears got worse despite the reassurances of my primary care doc WHO WAS A HEMATOLOGIST (!) that everything was fine. I eventually did an intensive run of CBT and got my fears under control -- not that I'm cured of HA, but it's a lot calmer.
About three months after my CBT ended, I was walking downtown (in the suburb of San Francisco where I live) when I passed a restaurant hall full of people listening to a woman giving a PowerPoint presentation. At the very instant I looked in (it was night time), she pulled up a slide describing the exact same form of blood cancer that I had been obsessing about! She was clearly talking to a bunch of medical professionals about recent treatment advances. Had I still been in the grip of my HA, I would have thought, "Oh, that means I MUST have it. What else could it mean?"
But by then, I was able to recognize it for what it was: A coincidence. If I hadn't gone down the rabbit hole of learning about the disease I just KNEW I had, I probably would never have noticed what was on the slide. I would have glanced in and kept on going. I might not have even registered the words. I recognized the name of the disease only because I'd been thinking about it so much!
So, yep, we see what we're thinking about and we think too much about what we see.