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WSN/33 Diversity in Korean Swine
December 21, 2004
Further analysis of the WSN/33 isolates in Korean swine has indicated that the human sequences are probably widespread. In addition to the two H1N1 isolates, there are 4 H9N2 isolates with WSN/33 sequences.
However, each of the H9N2 swine isolates is unique. One, A/swine/Korea/S109/2004 (S109), has WSN/33 sequences in all six internal genes, although the 3' end of PB2 is avian. Another, A.swine/Korea/S83/2004 (S83) has WSN/33 sequences in only 3 internal genes. However, the two isolates with WSN/33 in 4 genes, A/swine/Korea/S81/2004 (S81) and A/swine/Korea/S190/2004 (S190), have very distinct NA genes.
There are at least two distinct avian H9N2 strains with WSN/33 sequences. Both are related to each other and earlier Korean H9N2 isolates. One is represented in the H9N2 swine isolate without WSN/3 sequences A/swine/Korea/S452/2004 (S452), which is very similar to the chicken isolate from last year, A/chicken/Korea/S1/2003 (S1). The other group may be more like the two chicken sequences on deposit from this year, A/chicken/Korea/S20/2004 (S20) and A/chicken/Korea/S22/2004 (S22).
The 4 swine isolates with WSN/33 sequences have at least 3 distinct NA genes. S81 has an NA like last year's chicken sequence, S83 is like this years chicken sequences, and S109 and S190 have an NA that is a recombinant between the two chicken sequences.
Thus, all 4 H9N2 swine isolates with WSN/33 sequences are unique, indicating that there is considerable diversity in the swine WSN/33 isolates and that the infections are quite widespread and quite real.