It cites this research article just posted in the research journal PLoS ONE.
Here's a brief sample from an article by writer James Fischer titled "A More Concise Explanation of CCD-Iridescent Virus and Nosema ceranae":
A multi-institutional team of researchers sifted through the ever-growing zoo of new invasive, exotic pathogens of bees, and consistently found the same two disease organisms in beehives suffering from Colony Collapse Disorder (CCD) in samples collected from 2006 to 2009.
They discovered a new virus never seen before in North America, and found a well-known invasive variant of the intestinal bee disease Nosema. The overlooked virus may explain why prior studies presented mutually contradictory findings. This new evidence could create a basis for consensus among research teams who to date, lacked common ground in their conclusions.
If you're wondering why you should care about any of this, just remember that something like one-third of diet comes from crops grown thanks to bee pollination.
On a side note, I just harvested roughly a few gallons of honey from my hive this past weekend. Here's a feature I wrote around this time last year on becoming a beekeeper and our local bee scene.