All three of ours sleep in our bed and we have no issues besides getting licked in the face once in a while in the middle of the night. LOL
To avoid middle of the night distress if one of them does happen to get sick, we keep a piece of fleece on the last 1/4 of our bed near our feet. They rotate all over the bed , of course, but as luck would have it if anyone has gotten sick its been on the peice of fleece so I didn;t have to wash our nice cover.
We're very careful with what ours eat so *knock on wood*...no one has gotten sick in quite some time.
Its much harder to control though once the weather warms up and they get to run freely outside. You never know what they might pick up and if you have more than one its a bit harder to keep a keen eye on all at once