The fungus Glomerella cingulata can infect both azaleas and Camellia japonica. When it infects these plants, it is likely causing canker. It is in the sexual stage when it infects. Here are some general links: http://en.wikipedia.org/wiki/Glomerella_cingulata http://en.wikipedia.org/wiki/Anthracnose
So to answer your question, if they are reasonably close by, then it seems like a real possibility that the fungus could spread. GOOD LUCK!
Hope that helps!
Thank you very much plasmodesmata! That’s a big help. The camellias had to go, couldn’t get rid of it and it was spreading. Now I see those same cankers on an elderly azalea. Hope I can save it, there’s a whole row of those poor old things…