Most common rubrus (raspberry/blackberry) viruses send the leaves a mottled yellow colour. That includes raspberry mosaic virus and raspberry leaf spot so this isn't like that. Don't worry about the fact that I refer to raspberries, the tayberry is a rasp/black hybrid which can get the same diseases.

When did this appear uulwyn? If recently it could be just a touch of the frosties, if it appeared last summer it is more likely to be caused by an aphid attack. So that doesn't occur again, then spray with any aphid killer if you use chemicals. Invest in a biological control if you don't. Either way I would take off and burn (don't compost) the infected leaves and have a good look next year when aphids appear again.

__________________
Why didn't Noah just swat those 2 greenflies?

Why are they called apartments when they are all stuck together?
>
>If flying is so safe, why do they call the airport the terminal?