Mildew on Viburnum Tinus

I've bought an anti-fungal spray but don't know if it will cure existing mildew and restore the colour of the leaves. Or do I need to pick off the affected leaves and use the spray to keep the mildew at bay for the healthy leaves ?

I've never seen mildew in my garden before, it's really unsightly.  Does it prefer certain plants or could it spread to other shrubs ?

Thanks