Yes, very similar viruses can exchange bits of DNA. Two flu viruses infecting one person, or two strains of HIV. What us persnickety types are carping about here is that a bird flu virus was crossing with an MRSA bacterium. I'm trying to think of an example of the same thing on our scale, but I can't because there is less difference between, say, a human and an ant than there is between a virus and a bacterium.