REST! Most people who go to disney do alot more physical activity than thier bodies are used to. Start walking program a few weeks before your trip. Get your body used to spending alot of time outdoors in the hot sun. Take a rest break during the day to keep your energy levels up. Eat healthy meals while you are in the parks. Drink lots and lots of water all day every day. If you let your body get tired and worn out you will be much more suseptable to a bacteria or virus. if you want to stay healthy follow the habits of healthy people!