Oh my gosh I've been feeling the same way~
I'm currently 17 turning 18 and other than a bout of Rotavirus as a baby, no one in my family has ever caught it, not even my sister who's still only 12...my parents have said they don't even think they've ever caught it...and to say the least all four of us are blood type O...and before last year I was still emetophobic but didn't know about the existence of viruses and such...so I had very bad hygiene habits (from the eyes of an emetophobe that is, like eating in public without washing hands, not washing for at least 30 seconds after using bathroom), yet when my friend had it towards the end of the year I suddenly learnt of it and got very scared...I google my city with the words "gastro" or "flu" everyday just to check if any news reports have come out...ik that's really bad for anxiety but I just can't help it!