Some trees such as honeycrisp appear virus infected. I purchased my honeycrisp from a reputable orchard so I definitely know they are not any different from other honeycrisp. After a year of suspicion I realized it was due to natural problems with the tree http://articles.extension.org/pages/39083/i-have-a-honeycrisp-apple-tree-that-i-planted-in-my-back-yard-in-south-maplewood-last-year-this-year. Honeycrisp chloroysis will definitely have you concerned the first time you see it Commercial Production of Honeycrisp Apples in Ontario. Never had a virus yet but that’s the kind of thing that is concerning! It could have just as easily been apple mosaic. I’m equally concerned about bacteria as viruses. Let’s face it even bad fungal diseases are something I could do without! Our native wild cherries and plums are hosts to lots of stone fruit diseases. Viruses are out there so limit your scion sources but remember even being as careful as you can be it could happen. Things like cicada spread bacteria or any disease like wild fire. I experienced the 17 year cicada personally and saw it spread fireblight but thank God is was not a virus.
17 year cicada's woke up hungry
Late season Fireblight