Bird flu genes found in new swine flu
The new strain of swine flu has a molecular twist: it
is composed of avian and swine influenza genes.
The swine flu has been identified by researchers as a new strain of swine
influenza - H2N3 - which belongs to the group of H2 influenza viruses that last
infected humans during the 1957 pandemic.
Research Service (ARS) veterinarians conducted this research with a group of
other scientists from around the country. The veterinarians of the ARS, the US
Department of Agriculture's chief scientific agency, work at the agency's
National Animal Disease Center in Ames, Iowa.
Avian related unknown pathogen
The research team
studied an unknown pathogen that in 2006 infected two groups of pigs at separate
production facilities. Both groups of pigs used water obtained from ponds
frequented by migrating waterfowl. Molecular studies indicated the unknown
pathogen was an H2N3 influenza virus that is closely related to an H2N3 strain
found in mallard ducks. But this was the first time it had been observed in
Influenza viruses have eight gene segments, all of which can be swapped
between different virus strains. Two of these gene segments code for virus
surface proteins that help determine whether an influenza virus is able to
infect a specific host and start replicating - the first step in the onset of
In the newly isolated swine H2N3, the
avian H2 and N3 gene segments mixed with gene segments from common swine
influenza viruses. This exchange - and additional mutations - gave the H2N3
viruses the ability to infect swine. Lab tests confirmed that this strain of
H2N3 could also infect mice and ferrets.
These findings provide further evidence that swine have the potential to
serve as a 'mixing vessel' for influenza viruses carried by birds, pigs and
It also supports the need to continue monitoring swine -
and livestock workers - for H2-subtype viruses and other influenza strains that
might someday threaten swine and human health.
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