First of all, take care of yourself in the weeks leading up to your trip. It's easy to get run down trying to tie up all the loose ends before a vacation and that just makes you more succeptible to illness. Get plenty of rest and take vitamins. Keep your immune system running at it's best.
Yes, I had a solo trip at WL about five years ago and got the fever and chills flu. The funny thing is, I was checking in the Wednesday before Thanksgiving (for a ten day trip) and since the hotel was busy and I was solo, they put me in an accessible room right around the corner from Roaring Forks. I remember thinking how huge the bathroom was, and being glad I had such a nice shower. About three days before check out, I became ill. I had brought over the counter medicine with me, which I was very glad to have, but what I really wanted was something hot to drink. This was back before the coffee makers and fridges were standard in the deluxe resorts. I had an electric cooler full of cold drinks, so I didn't get dehydrated, but I wanted something hot soooo bad! I didn't let mousekeeping in at all that first day I was sick. I was so thankful for the grab bars in the bathroom, because I was so shaky I could hardly walk. By the second day, I had enough energy to sit on the pull down seat in the shower (by now I was thanking God I was in that accessible room) and get cleaned up so I could go to Roaring Forks for some hot soup. It's one of the few trips that I used luggage assistance when checking out.
I've made many solo trips since then, and not had a problem. One thing, I became a fanatic about hand washing. I carry a lot of individually wrapped towelettes with me and use them often. I always wash right before eating (I used to stop in the restroom to wash before going to a restaurant - not thinking about how many things get touched between the restroom and actually dining) and I make sure I don't touch my face without washing first. I haven't been sick once at Disney since then. I continue to pack enough over the counter flu, sinus/allergy, and pain medicine to get me through four or five days, just in case.
If you are staying in a value resort without a coffee maker, I would recommend taking one of those small immersion heaters with you, as well as an old cup (one you don't care if it breaks, or buy a souvenir coffee cup on the trip), so you can make something hot to drink. I was so desperate for something hot to drink that time at WL that I would run the tap water until it got hot and drink that. Not the most wonderful drink, I can tell you. But if you've got a couple teabags, or a couple packets of instant chicken soup, along with that immersion heater, it can make all the difference. Now that there are coffee makers in the deluxe and mod resorts, that is a big help.
Fortunately, I haven't had to deal with a stomach virus at Disney. I do use the Bonine motion sickness medicine, which can also be used for virus nausea, because I get motion sickness on the rides. So I probably wouldn't feel any minor stomach upset. I do travel with some Pepto Bismol chewables, in case I have a stomach issue, but so far, I haven't had to use them.
Don't be afraid to call the front desk if you need help. Oh, and don't be alarmed when mousekeeping shows up after you've kept them out for a day or two, wearing rubber gloves, face masks, and looking like a hazmat team!
It happened two years earliler in Las Vegas, as well. *sigh*
Luckily, I haven't had any major ones since having my son 6 years ago but once you've been through it, it's always in the back of your mind! It's a constant worry that I'll be walking through a park and suddenly have an attack - can't move, can't walk ... it's like a knife cutting from navel to down yonder. The only thing that can alleviate the pain is a combination of demerol/morphine and gravol. What should I do if this happens? 
). Thank goodness I haven't had a bad attack in years, but one of my very first attacks happened when standing in line for Indiana Jones at DL. When the dizziness got so bad I could barely walk or hold my head up, I went to First Aid and they sent me any my friend to a local ER in their own quasi-ambulance. Several hours later after it was under control and the hospital released me, they brought me back to Guest Services where we got passes to come back another day and were driven right to our car. 
