Pandemic Worry as Avian Genes Found in Swine Flu Strain

US - The discovery of a new strain of swine influenza — H2N3 — is cause for concern, say scientists as it proves that swine have the potential to serve as a “mixing vessel“ for influenza viruses carried by birds, pigs and humans.
calendar icon 19 December 2007
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The virus belongs to the group of H2 influenza viruses that last infected humans during the 1957 pandemic. It was discovered by Agricultural Research Service (ARS) veterinarians at the National Animal Disease Centre, Ames, Iowa. They believe it is further evidence that pigs could pose a serious risk to human health unless measures are put in place to monitor H2 related viruses.

They say that the continual surveillance of swine and livestock workers for H2 subtype viruses and other influenza strains is vital. Lab tests have already confirmed that this strain of H2N3 could also infect mice and ferrets.

The research team, with support from scientists from the Iowa and Minnesota Universities and St Jude Children’s Research Hospital, 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.

Species transfer

Further molecular investigations indicated that the unknown pathogen was an H2N3 influenza virus, and closely related to an H2N3 strain found in mallard ducks. This was the first time this avian flu virus had been observed in mammals.

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 influenza infection.

The newly isolated swine virus is composed of both avian and swine influenza genes along with other genetic segments from common swine influenza viruses. This exchange — coupled with additional mutations — gave the H2N3 viruses the ability to infect swine.

The veterinarians and scientists credited with this discovery are: ARS vets Juergen Richt, Amy Vincent, Kelly Lager and Phillip Gauger; research scientist Wenjun Ma,Iowa State University (ISU), veterinarian (ISU) Bruce Janke and colleagues at the University of Minnesota and St. Jude Children’s Research Hospital.
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