Cat Flu?

I'm sure cats do get the flu just like we do.

My cat, my baby whom I've had for 8 1/2 years, has been very sick the past few days. First he was just hanging around the house more often than normal (he's an outdoor cat, likes to be inside but not for too long). Then 2 days ago he was just very lethargic, wouldn't eat. Fred and I brought him inside and let him sleep in our bathroom, and that's when I found out he was pretty sick. He wouldn't eat, and barely drank any water. And (pardon my graphicness of this) I awoke to diarrhea all over my toilet room floor.
Yesterday he spent outside, but he stayed on our patio all day. I felt very bad leaving him outside, it was pretty cool and rainy, but I'm such a wimp when it comes to cleaning stuff like that up. I have a very weak stomach and a horrid gag reflex and just can't do it. I mean, I even gag brushing my teeth, and I don't even brush my tongue all the way to the back to cause it!

Anyway, I was checking everything outside for the night to lock up and go to bed, when who do I see on my back doorstep? Semper Fi!! He was home!
He looked up at me and meowed and purred and I was so happy! I talked to him a bit and he talked back, and I ran inside to get Fred.
He's sleeping in our bathroom again tonight. He's a little messy (read above to what I woke up to), but I'm sure he'll clean himself up good when he's fully recovered. I thought I was losing him to old age (they say a cats lifespan is reduced if they are outdoor cats), but he's fine now. I hope he lives to a ripe old 20 years. :)
Here is a picture of him. This one is a few years old. I took it with my Minolta DiMage, playing with settings and stuff, in my bed.