Pests and Diseases
Imagine having a bug the size of a dinner plate on your back, which bores a hole in your flesh. The bug then sucks out your blood and spits back blood and possible infections from someone else into the hole on your back. Nasty.
That's Varroa. You must be able to manage varroa in your bees, if you want to be a beekeeper.
Keeping bees is like keeping other animals. You are responsible for their well-being and must be aware of how to keep them healthy.
There are many diseases of honey bees. Some of these are 'notifiable', like other livestock diseases.