How does American foul brood primarily affect honey bees?

American foul brood is a serious bacterial disease caused by the bacterium Paenibacillus larvae, and its primary impact is on young honey bee larvae. When honey bee larvae consume food contaminated with the spores of this bacterium, they become infected. This disease specifically targets larvae that are less than three days old, leading to their death, typically after they are sealed in their cells. The infection can have devastating consequences for a colony, as it effectively eliminates potential future worker bees before they can develop and contribute to the hive's functioning.

While adult bees and the queen bee interact with the larvae and can be affected indirectly by the overall health of the colony, the defining characteristic of American foul brood is its direct lethal effect on young larvae. Therefore, the emphasis on the impact of the disease on larvae is what makes this answer the most accurate in this context.