It's a virus but one that seldom damages the camellia other than marking the leaves.

Whoa. is there anything I can do about it?

Not really. There is nothing that can be used. Probably because it does not damage the plant. Some viruses produce white streaks, others produce yellow streaks. During Xmas 2012, I went to a local nursery to check their camellia stock and they had some for sale exhibiting yellow streaks. So it is a little "common" to see that. If it is not your cup of tea, the only thing you can do is replace the shrub.

I don't mind at all. As long as it is not harmful to the plant itself or to other plants, I don't mind the streaks. Does anyone know if this will go away, or is it permanent? I had read somewhere that there was some other camellia virus, but that it goes away after 5 years (??!).

Some of these camellias with streaks are known to disappear after a few years but not all. No one really understands the exact process well so when the plant develops streaks, you have to wait and see. I can imagine what a pain this would be to persons trying to sell or register the camellia as a "new" variety! If it is not somewhat stable, you cannot recreate it easily on other plants.

The two suspects are viruses and genetic changes. Camellia blight fungus is also known to stay dormant in the soil for up to 5 years.

Hey all - thanks so much for your answers on the virus. Does anyone have any suggestions on how to go about pruning this, if it's necessary? Thanks!

Here is a good article on pruning by the American Camellia Society. I usually find that I have to do minimal pruning thru the year; only if you are doing an espalier or if you plant it where it will exceed its size at maturity does camellia pruning become a true gardening chore.

Here is a link that might be useful: Pruning by the ACS