TORONTO - The flu virus retrieved from a pig on an Alberta farm closely matches the swine flu viruses that have been retrieved from humans, an expert in genetic sequencing said Friday.
The genetic blueprint of the H1N1 virus, decoded at the Canadian Food Inspection Agency's National Centre for Foreign Animal Diseases in Winnipeg, was posted Thursday in Genbank, on an open access genetic sequence database maintained by the U.S. National Center for Biotechnology Information.
The Canadian Food Inspection Agency would not answer questions Friday about the posting of the genetic sequence or the agency's analysis of the sequence data.
But Steven Salzberg, director of the University of Maryland's centre for bioinformatics and computational biology, examined the sequences of two of the genes at the request of The Canadian Press.
"It's 99 per cent identical to one of the Mexican sequences," Salzberg said of the genetic code for the hemagglutinin, the gene that gives the virus the H in its name.
The hemagglutinin is considered the most important gene in the virus; it is the one that must lock onto the cells of the respiratory tract to initiate infection. It is also the gene most prone to mutation, because it has to evolve to evade the human immune system.
Salzberg also looked at the genetic sequence for PB1, which is the single gene in this unusual hybrid virus that derives from human flu viruses. It too closely resembles the ones that are now spreading in at least 34 countries.
"It's definitely the same strain. From looking at these two (gene) segments, it's clearly the same strain. Ninety-nine per cent identical. That's what they all are," Salzberg said.
The discovery of this novel virus in pigs in an Alberta farm was the first and to date only finding of the virus in pigs.
Despite the fact that the virus is the offspring of two swine viruses which may have reassorted in pigs, it has not been found to be spreading among pig populations. And officials do not believe pigs are playing a role in its continued spread; at this point, the virus is a person-to-person pathogen, they say.
They are, however, keen to keep the virus from becoming entrenched in pig populations because of the risk it might acquire further mutations if given the chance to cycle back and forth between people and pigs.
It is believed the virus was introduced to the farm -- a closed operation near Rocky Mountain House, Alta., -- on April 14 by a carpenter who had just returned from Mexico.
The carpenter, who was only tested after he had recovered, tested negative. In fact while a number of people on the farm were reportedly ill around the time the pigs were sick, so far none of the humans on the farm have tested positive for the virus.
Last week Alberta's chief veterinarian announced that 500 pigs from the farm were to be culled to ease overcrowding at the operation, which remains under quarantine.
