My parents went on a two week vacation to Switzerland and have been back in the United States for around a week. In the last few days they've gotten very sick. The symptoms seem like covid or the flu, but my dad said their doctor ruled those out as well as strep throat. I'm sure they ran additional tests as well. Has anyone heard about something like this going around? Should I be concerned? FWIW I've been around them the entire time they've been sick and I haven't caught anything.