Cabernet Sauvignon showing Yellow Speckle Virus. It shows up in some seasons by giving some leaves a yellow 'spray paint' look.
This is a common virus, like leaf roll which only has minor effects on the vine. In most cases you cannot notice any difference between clean and infected vines unless they have the speckled leaves. In trial work in the 1990's it reduced yield by 23%. http://www.ajevonline.org/cgi/content/abstract/43/1/31
Once vines have a virus, it continues for the life of the vine. Also any cuttings taken and propagated from these vines will have virus. It is best to get virus free cuttings when grafting or establishing a new vineyard.