In the wild, dogs shun sick dogs. It's the way of the pack, so for one doglet to distance themselves from another who is not well is natural, and it's perfectly acceptable dog behaviour. It's weird to us, and seems downright cruel, but that's because we have attached emotions to our actions, whereas dogs do not.
Rosie will not come near me when I am ill. Even though I am pack leader in our household, it's the way of the pack, and I don't judge her for it (even tho a cuddle would be lovely when you are down and grizzly). She knows when I am on the mend before I do tho, as her comapny returns to its normal level.