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WSN/33 / H9N2 Recombination and Reassortment in Swine
December 15, 2004
The lab isolating the swine sequences has not knowingly had WSN/33 anywhere in the lab. The swine isolates were isolated in chicken eggs and the MDCK cells in the lab are PCR negative for WSN/33.
Further analysis of the H9N2 sequences indicates that there are at least 3 distinct H9N2 sequences that have recombined and/or reassorted with the WSN/33 sequences, Each set of WSN/33 sequences also has unique polymorphisms which follow well defined rules of influenza virus evolution and emergence.
The likelihood of these WSN/33 sequences being a lab artifact is very close to zero. The path from a lab to at least 6 swine on several farms in South Korea is still unclear, although all of the H9N2 sequences from WSN/33 positive isolates are closely related to each other, as well as recent H9N2 chicken and swine isolates from South Korea.