A ProMED-mail post (July 23, 2009)
Two Canadian Food Inspection Agency [CFIA] inspectors appear to have contracted swine flu while investigating an outbreak of the new virus in pigs on an Alberta farm in late April , the agency confirmed on 21 July 2009.
The cases appear to be the first report of people catching the new H1N1 virus from pigs.
While the pandemic virus is of swine origin, it was found in people first. Pigs are not currently believed to be playing a role in ongoing transmission of the virus.
The agency said in emailed answers to questions that it’s impossible to say with 100 per cent certainty that the inspectors were infected by the animals. But the infections took place in the early days of the swine flu outbreak, when few cases were being reported in Canada. It’s known that the men did not use proper safety techniques while in the barn, apparently removing the N-95 respirators that covered their noses and mouths because they were hot. “We conducted a review of the situation and determined that CFIA protocols for personal protection were not fully observed in this case,” the agency’s email said.
The agency said it doesn’t intend to change protocols for conducting this type of investigation because its existing protocols, if complied with, would have been adequate to protect the workers.
“Supervisors are being asked to ensure inspection staff have received the appropriate training and understand the procedures before being assigned to the investigation.”
The Alberta pig farm incident was the first report ever of this new virus being found in pigs. The source of the infection in the pigs remains a mystery and the handling of the case has been anything but smooth.
Officials at first identified a carpenter who worked briefly on the farm while ill with flu-like symptoms as being the source of the infection. But the man, who had recently returned from a trip to Mexico, was later told tests showed he was never infected with the new virus.
There were reports that members of the farm family were also sick shortly before the pigs started showing symptoms. But samples taken from them were not adequate to confirm or dismiss them as possible sources of the infection. Officials now admit they’ll likely never know how the virus was introduced into the herd.
Argentina recently reported two more cases of person-to-pig transmission of the new virus.
Influenza experts are not surprised the virus can infect pigs and pass back from them to people. But they worry that if this type of ping-ponging occurs, it will drive the viruses to mutate.
It’s impossible to predict what the outcome of that type of evolution would be, but it could undermine the effectiveness of swine flu vaccine currently being developed for people.
Earl Brown, an expert in influenza virus evolution, called the trend towards increasing interspecies transmission of flu viruses “disquieting.” “When it was in Alberta, you had this virus of swine origin … and then you had the question: Well, is it now a human flu or is it a swine flu? And it’s clear that it’s both,” said Brown, a virologist at the University of Ottawa. He said there has been rapid evolution of flu viruses in pigs in recent years, as well as cases of avian influenza viruses, including the dangerous H5N1 virus, jumping into people.
In the influenza world, pigs are described as the mixing vessel, because they can be infected with both bird viruses and human viruses — giving rise to hybrids that they can pass back to people. “You just don’t want the pig to be the conduit for all these adapted viruses they’ve got from birds,” Brown said.
“I think the general trend is not good but this particular virus, you know it’s still an open book at to whether it’s going to tone down, or it’s going to become more like a seasonal flu fast, or if it’s going to ramp up. We really can’t predict and we’re just watching and trying to read the numbers.”