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Ontario Swine Flu Related to British Columbia Bird Flu
January 3, 2005
Two H3N3 Ontario swine flu isolates, A/swine/Ontario/K01477/01(H3N3) and A/swine/Ontario/42729A/01 (H3N3) have become publicly available at GenBank. The isolates contain genes that are most closely related to avian influenza (bird flu) isolates from North America.
The H3 is most closely related to avian H3 such as A/mallard/Alberta/199/99(H3N6) or A/pintail/Alberta/37/99(H3N8) although there is also relatively high homology with seal who died of pneumonia along the cape Cod peninsula of Massachusetts in 1992, A/Seal/MA/3911/92 (H3N3) and A/Seal/MA/3984/92 (H3N3).
The N3 however is most closely related to avian isolates from Texas, A/blue-winged teal/TX/2/01(H7N3), New Jersey, A/ruddy turnstone/NJ/2242/00(H5N3) as well as British Columbia A/GSC_chicken/British Columbia/04(H7N3), A/GSC_chicken_B/British Columbia/04(H7N3). The British Columbia isolates were from the devastating infection in Fraser Valley last season.
Four of the remain six genes, PB2, PB2, PA, NP also had close homology with the 2004 isolates from British Columbia. The other two genes, MP and NS, were also related to avian genes from the Northeast coast of the US or Ontario, Canada, respectively.
These isolates were distinct from the H3N2 swine isolates that were similar to the recent H3N2 turkey isolates from Minnesota, North Carolina, Ohio, and Missouri. In those cases the H3 is closely related to human H3 from patients infected in the mid to late 1990's. The N2 is closest to H1N2 swine isolates from North America and Korea, which is related to human N2 from infections in the mid-90's.
The swine isolates with homology to contemporary human isolates are quite distinct from the recent H1N1 swine isolates in Korea. The H1 and N1 come from the 1933 human lab virus WSN/33, as do 5 of the other 6 genes. In the Korean H1N1 isolates, only PB2 is from a Korean avian H9N2 source. The WSN/33 genes are also found in 4 additional H0N2 swine isolates.
Although the sequences of these isolates have been made public for over a month, there has been no official announcement on the significance of these sequences.