I had measles when I was in high school, during the late-1980s. I had been vaccinated during infancy, but I was told that the vaccines were given too early back then, and weren't sufficiently effective. Quite a few other people at school also had measles. The county health department came out to my house and did a blood test, to verify that it was indeed measles. After I returned to school they came there and took another one, to verify that I was no longer sick. (I hate needles.)
I remember it felt like a cold coming on, and then one day I woke up covered in spots. (It happened to be the same morning that I was supposed to take the SAT -- which I went ahead and did.) It wasn't until several days later that I actually felt sick. It's worse than a cold, but not as bad as the flu. It kind of fucked up my hearing in one ear, though.