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There seems to be a definite knowledge gap with regard to avian influenza. Comments on sequences of H5N1 from swine have raised issues of infectivity of the virus. The virus has already left it signature in the bodies of dead patients in Vietnam and Thailand.
The virus appears to be several steps ahead of investigators. The codon rules are quite precise for avian flu and certain molecular signatures indicate where (location and species) the virus has been and the lethal isolates from patients have signatures indicating the virus has been in mammals (people and/or pigs).
The potential lack of infectivity of H5N1 isolates from swine is merely wishful thinking. As far as mixed infections between H5N1 and H3H2/H1N2/H1N1 are concerned, the virus is clearly in the "been there, done that" category.
The story is in the sequence, and the human/swine signatures in H5N1 from fatal cases in Vietnam and Thailand are very real.