Really sucked that this couldn't have been on a weekend or even a friday
Don't you have the flu tomorrow? You are probably starting to feel kinda bad right now, right?
Starting practicing your voicemail now:
If needed-to coworkers/boss covering for you: (beep 4 coughs hacking style and a sneeze . . . raspy barely audible voice), "Hey I just wanted to let you know" (clear throat loudly as if hacking up both lungs) "I am really sick, I am gonna take one for the team because I don't want you all to catch what I have, I'll see you next (blow nose loudly) . . . week" . . . hang up, but rattle the phone around like you can barely reach the phone cradle (note call from landline to avoid any suspicious thoughts that you didn't actually make it home).