Wikipedia has a list of diseases affecting bees here: HERE - there are many.

From the above article regarding CCD:

Colony Collapse Disorder (or CCD) is a little-understood phenomenon in which worker bees from a beehive or Western honey bee colony abruptly disappear. CCD was originally found in Western honey bee colonies in North America in late 2006.[25]

European beekeepers observed a similar phenomenon in Belgium, France, the Netherlands, Greece, Italy, Portugal, and Spain,[26] and initial reports have also come in from Switzerland and Germany, albeit to a lesser degree.[27] Possible cases of CCD have also been reported in Taiwan since April 2007.[28]

The cause (or causes) of the syndrome is not yet well understood. Hypotheses include environmental change-related stresses,[29] malnutrition, pathogens (i.e., disease[30] including Israel acute paralysis virus[5][31]), mites, pesticides such as neonicotinoids or imidacloprid, radiation from cellular phones or other man-made devices,[32] and genetically modified (GM) crops with pest control characteristics such as transgenic maize.[33] Some claim that the disappearances have not been reported from organic beekeepers, suggesting to some that beekeeping practices can be a primary factor.

My local beekeeper has been managing to keep most problems in check - this year, for the first time ever, he had some problems with beetles getting into the hives.