There are a number of infectious diseases and parasites that can have serious consequences for a bee colony.
Among them are:
*Nosema - a fungal infection that affects the adult bees intestinal tract
*Chalkbrood - a fungal infection that affects the brood, ultimately killing it
Stone brood - a fungal infection that affects the brood, ultimately killing it
*[[Varroa]] - a parasitic mite that often leads to secondary infections, such as a number of viruses, that end up killing the colony over the course of a few years.
Detailed descriptions of these diseases that affect all honey bee subspecies can be found for example [https://en.wikipedia.org/wiki/List_of_diseases_of_the_honey_bee here]