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Were it not for concerns over the potential for the pandemic H1N1 virus to acquire additional genetic changes via reassortment, the discovery of the virus in swine would be a non-story by now.
After all, as a swine-origin influenza virus, novel H1N1 is understandably pretty comfortable in a swine host.
Just yesterday we saw a report of a 16th pig farm in South Korea reporting the infection. In recent months farms in Europe, North and South America, and Asia have all reported livestock infections.
Pigs are susceptible to a variety of human, avian, and swine influenza viruses. They can even be infected by two different flu viruses at the same time.
As such, they are considered to be good `mixing vessels’ for viruses, and could help produce a hybrid `reassorted’ virus. One that could potentially have pandemic potential.
Of course, that’s a pretty rare occurrence.
You not only need two compatible flu viruses to inhabit the same cell at the same time, it needs to produce a `fit’ hybrid. One that replicates well, is adapted to human receptor cells, and is easily transmitted.
It appears that our 2009 pandemic virus bounced around in pigs for many years, picking up multiple mutations (via reassortment), before it found the right combination to jump to humans.
It could take years, perhaps decades, before we see that sort of thing happen again.
Or it could happen tomorrow.
The infected swine detected in this report from Hong Kong came from the Chinese mainland where little or no testing occurs, and bio security on farms often leaves much to be desired.
Other influenza viruses, including the H5 and H9 avian viruses, are also known to circulate among domesticated livestock in that region, and that has some scientists concerned.
The good news here is that testing so far has shown no gene reassortment to have occurred, and the virus detected remains genetically similar to the H1N1 pandemic virus.
This from News.gov.hk.
Pigs test positive for human swine flu
December 30, 2009
The University of Hong Kong's influenza virus surveillance programme found five samples taken from pigs at the Sheung Shui Slaughterhouse on December 17 tested positive for the human swine influenza virus, the Food & Environmental Hygiene Department said today.
This is the third time the programme uncovered positive samples. No gene reassortment has occurred and the virus remained genetically similar to the human swine flu viruses regularly found in people. The flu virus is believed to have been transmitted from people to pigs.
The concerned samples were taken from pigs imported from the Mainland. The department informed the Mainland authorities, and they have strengthened monitoring of registered farms that supply live pigs to Hong Kong.
The World Health Organisation, World Organisation for Animal Health, Food & Agriculture Organisation of the United Nations and World Trade Organisation state that pork and pork products which are handled properly and thoroughly cooked are not a source of human swine flu infection.
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