CDC Briefing on Public Health Investigation of Human Cases of Swine Influenza

we believe at this point that human-to-human spread is occurring. That's unusual. We don’t know yet how widely it's spreading and we certainly don’t know the extent of the problem.We're also working with international partners to understand what may be occurring in other parts of the world. And we particularly want to get the messages to clinicians today.

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clipped from www.cdc.gov I want to tell you a little bit about what the laboratory ahs found from exploring this particular strain.  CDC has conducted testing on all seven samples and we've determined that they are swine influenza A, H1N1.  These are human infections with swine influenza viruses.  These are viruses that usually infect pigs but in this case we're finding the illness in people.  Preliminary testing of viruses from the first two patients shows that they are very similar.  Additional testing is ongoing with the newer isolettes.  We know so far that the viruses contain genetic pieces from four different virus sources.  This is unusual.  The first is our North American swine influenza viruses.  North American avian influenza viruses, human influenza viruses and swine influenza viruses found in Asia and Europe.  That particular genetic combination of swine influenza virus segments has not been recognized before in the U.S. or elsewhere.