Ping for Niman's take on all this:
http://www.recombinomics.com/whats_new.html
Virus moving via recombination.
From Niman's site:
H5N1 has been evolving via recombination. The changes are small but frequent. Currently, there are at least four different versions of H5N1 bird flu circulating. Clade 1 has caused reported human fatalities in Vietnam, Thailand, and Cambodia. For clade 2, there are at least three distinct versions. One is in Indonesia. Most of the human cases in Indonesia have a novel HA cleavage site that has not been reported in any avian isolate. In the current paper discussed above, the Indonesia/5/05 isolate was detected in respiratory secretions of infected ferrets. A second clade 2 version is the Fujian strain, which is represented in all public human isolates from China in 2005 and 2006. Thus strain has also been detected in birds in Laos and Malaysia. The third clade 2 strain is the Qinghai strain, that is being transported and transmitted worldwide by migratory birds. There are multiple versions of this strain, but it has cause human fatalities in Turkey, Azerbaijan, and Egypt and has also caused a human infection in Djibouti.
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My take on this: the scientists have tried to mix one strain with another strain in ferrets. Nature has the opportunity to try recombination millions of times. Frankly, I'd put my money on Nature.
Just my opinion.