One thing I have learned the hard way through the years is that when it comes to careing for those who cannot tell you something is wrong, you need to learn what can go wrong BEFORE it happens.
Bees depend on their beekeeper to be vigilant and help them avoid calamities before they happen. If we wait until the evidence of a disease is obvious, or worse, don't know what to look for and so notice nothing, it will usually be too late to help much.
To that end I am using these chilly months to refresh my knowledge of bee diseases so that I can head them off in time.
Here's one problem with my winter hive that was not so tough to solve.
If you are using your winter wisely and sharpening your bee skills too, I would suggest a perusal of my "bee resources page" where I have compiled links to several useful sites and videos on bee diseases. I have also recently found this concise pamphlet on honey bee diseases.
And remember: an ounce of prevention...