I just had aphids on a new orchid a week ago. Icky! I've no idea how far they can jump, but I know they can spread. They aren't tough to get rid of though.
I immediately seperated it from the others. I mixed up a neem oil & water solution (the neem oil container should have the proportions) and sprayed the orchid heavily with it, wiping off the dead aphids after it sat a bit. I poured more of the solution thru the bark, and I inspected the plants it had been near. I did not see any signs on them, but I sprayed them lightly too. Today, a week later, I inspected everything again, and saw no signs of them. However, I sprayed it again, and left it seperated. So far so good. After 3 weeks of no signs of bugs, I will let it rejoin the others.
Mini orchids on stick...I soak mine in a cup of water for 5-10 minutes, and then hang back up.