H5N1 Instability and Recombination

>>A small segment of the mother's virus has already been genetically sequenced, and matches viral samples taken from Thai poultry, Thai health officials said, suggesting that the virus may not have evolved dramatically yet. <<

 The above result sounds like the results obtained in Vietnam.  In late July early August a similar cluster of cases was observed in Hau Giuang in southern Vietnam.

 Like the cluster in Thailand, the caregiver (the initial victim's sister) developed symptoms 1-2 weeks after the initial case.  She too was confirmed to have been infected with H5N1.  Recent sequence data from chickens in Hau Giuang have been virtually identical to Vietnam isolates from the beginning of 2004.

 However, isolates from Thailand and Vietnam have already recombined, and the mammalian polymorphisms were present in early 2004 isolates from both countries.  In many instances, the polymorphisms in Vietnam and Thailand are not found in other H5N1 isolates, but are found in H1N2 isolates (most frequently isolated from pigs and people).

 The recombined isolates have already been shown to have an expanded host range as seen in isolates from wild and domestic cats, as well as experimental animals such as mice.

 More recombination may be required to achieve more efficient mammalian infections, but the growing instability of the H5N1 genomes in Asia, coupled with dual infections in wild birds, provided fertile ground for additional instability and recombination.