In November we will take our 30th cruise. Until recently we ALWAYS seemed to get a bad cold while on board. During the last two cruised I have carried a small bottle of hand sanitizer, like "Purel", and an air sanitizer for the cabin.
When you think about it: In the buffet line, 1000 people touch that same spoon! And-- there are 1500 people in a closed environment.
We just use the sanitizer before we eat each meal, and I spray the cabin each morning and night. It seems to work and sure beats getting sick!