I've been diagnosed with cytomegalovirus.
Apparently, it's really common and not a big deal, but it sounds impressive and I can probably use it as an excuse to take a few days off.
Sorry boss, my cytomegalovirus is acting up and I'm not going to make it into work.
They tested me for a bunch of different viruses, one of which was Cat Scratch Fever. That would have been even better to call into work with.
Sorry I'm late boss, I got too close to a catnip mouse and next thing I knew, it was an hour later and I was swatting at imaginary flies. meow.