Ben Sharvy wrote:
..............................
The currant isn't susceptible to the disease at all. It is strictly a
carrier...........................................

Well that certainly isn't true. Currants do get the disease and are
damaged by it. It may not kill the currant as it often does the white
pine, but it does get the disease.
I just did a search and the first site to come up happened to be from
the place where I spent the last 4 years of my college career:
http://ohioline.osu.edu/hyg-fact/3000/3205.html

In response to the previous poster, how could resistant currants still
spread the disease to the pines? The disease must live its life cycle to
continue. How can a currant that doesn't get the disease and doesn't
produce the orange fruiting bodies on the under side of the leaf spread
the disease to anything? If it's not producing the fungus spores, how
can the disease get over the the pines?

Steve