What is killing them? Everything from fungi, viruses, pesticides to cell phones have been implicated in their deaths which is often seen as an abandonment of the hive as bees seemingly go off to die. Specific causative agents include mites, the fungus Nosema apis, Israel acute paralysis virus, Invertebrate iridescent virus, the pesticide clothianidin, and cell phone radiation to name a few. While there may be multiple causes or perhaps combinational effects, it is unclear if there is any commonality among these deaths. None of the mentioned pathogens are infectious for humans.
Make no mistake about it, without bees, it will be a less colorful and fruitful world.