Some Canadian scientists clarified today that they still think it is "highly probable" that a farm worker infected the Alberta swine herd found that the virus now causing the swine flu outbreak in humans worldwide. But so far they have no laboratory evidence that the man suspected of transmitting the H1N1 virus in pigs first-pigs still found to harbor the virus had infected himself or even had the flu. Several other questions remain, including the number of infected pigs and if people who live or study the epidemic became infected.
Veterinarian Jim Clark of the Canadian Food Inspection Agency (CFIA) spoke with Science Insider today at length on the farm in Alberta, clarifying several points that were imprecisely reported here and elsewhere. CFIA and the Public Health Agency (PHAC) also provided details of the pig population at a press conference this morning.
The confusion begins with infected pigs. On May 2, the CFIA has revealed that he had found the virus in a herd of 2,0 pigs in Alberta. Although a scientific food safety World Health Organization said at a press conference May 3 that 220 animals had shown symptoms, Clark said that underestimates greatly spread throughout the herd. "The number of infections is between 75% to 80%," said Clark. This is based on 20 samples of pigs tested for the virus, of which 16 were positive.
From the outset, Canadian officials driven a farm worker as a likely source of transmission to pigs, which are in a "closed" flock. "There was no introduction of pigs in the herd for a very long time," says Clark. The worker farming has become the suspect "index case" of the epidemic in pigs returned from Mexicali, Mexico, on April 12 and returned to the farm April 14th. at that time, he had a flu-like illness. a subsequent analysis of two-thirds of the genome in 09 (H1N1) was isolated from more than a dozen of pigs shows that closely matches the human version of the virus. "viruses are very related to what is traffic in Mexico, "said Francis Plummer, head of the National Microbiology Laboratory, PHAC in Winnipeg, which has played a central role in identifying the virus. "I do not know how it could have got there."
But a report published yesterday by the European Centre for Prevention and Disease Control found that the worker had "tested negative" for the virus without explanation. Clark and Plummer said today that although the tests showed that the worker does not harbor the virus, which can reflect when he had a nasopharyngeal swab, the standard way to get a virus sample from people suspected of having the flu. "If I understand correctly, when this individual who had returned from Mexico was rubbed was a significant period of time after he was actually clinically ill," said Clark. "L anticipation of the end of public health is that they probably were not going to find any virus anyway, but they had to seize the opportunity to test it. "
Plummer said, it may be possible whether man has antibodies against the new H1N1 virus, that his lab is now looking at blood samples. "We think we'll probably be able to make a call based on the antibody levels in this individual," says Plummer. He noted that the antibody response induced by the new H1N1 swine virus "is quite a bit different 'response to the common "seasonal" H1N1 human. If this fails, Plummer said his lab may still be able to answer the question by looking at the T cells of man and analyze if they have immunological memory of having seen the new virus.
As a dizzying final twist to the story, people living on the farm, and investigators CFIA recently developed a disease flu-like, said Clark. All of them tested negative for the H1N1 novel, but again, some may have tested too late to find the virus, said Clark. "the people of the farm family who had an illness after this individual's income, it could have been because of exposure to it, but again, it may have been a seasonal influenza a virus that has absolutely no relation to the return of the worker Mexico, "said Clark. "Or maybe due to some transmission of the swine family farm."
So for now, no laboratory evidence linking the worker who went to Mexico for infection in pigs. "To say something definitively corroborated with laboratory information can not be done," said Clark. "All we can talk about is how we understand the situation based on events and when they happened and probability. To make definitive statements as to whether this person was the source of the virus, it is highly probable, but definitely, no, we can not say that. "
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