I have the flu. This miserable illness, that I've been informed is "going around," comes complete with nausea, headache, body aches, and exhaustion. It really hangs on too. I've had it for almost two weeks while some others have reported symptoms persisting up to three weeks.
My case was verified by a doctor, but before that it was a matter of matching symptoms with others I knew and saying "that really sounds like what I have." No, really. I was basing my professional diagnosis off the fact that my nurse, her mother, and I all had similar flu-like symptoms.