Swine flu has infected more than 9,800 people and killed 79 since it raised its snout on the global stage at the beginning of May, according to the World Heath Organization.
As soon as word spread like a virus in the global media, the meat industry piped up, saying that, as the problem was primarily in the human population, the name was misleading.
The WHO concurred soon after, announcing that we should all call the bug by the unpromising name of influenza A(H1N1) virus.
But for many scientists there are good reasons to keep the name swine flu.
Writing in the New Scientist, Debora MacKenzie explains, “This type of virus emerged in the US in 1998 and has since become endemic on hog farms across North America.”
Until then a normally mild form of swine flu existed in pigs, which didn’t show much sign of evolving. But in 1998 the virus “swine H1N1” mixed with human and bird strains, resulting in “triple reassortants,” first detected in Minnesota, Iowa and Texas.
It was a potent mix, with pig virus proteins making it a fast evolver, and the avian portion giving it quick replicating powers and therefore added virulence.
It is now entrenched in the North American pig population and there is evidence that thousands of farm workers have been infected with mild forms. “One in five US pig workers has been found to have antibodies to swine flu, showing they have been infected,” writes MacKenzie.
The current strain of A(H1N1) was first detected in humans in Mexico this year. Reports surfaced in early April that residents of a town called La Gloria, east of Mexico city, were hit by a surge in respiratory disease. After Easter week, when millions of Mexicans travel, new reports of the disease emerged across the country.
Residents of La Gloria blamed pig farms in nearby Perote owned by Granjas Carrol, a subsidiary of US hot giant Smithfield Foods, Mackenzie wrote.
Smithfield Foods denied any wrongdoing, citing its vaccination programme and monthly tests for influenza. But according to Mackenzie, “all the evidence suggests that swine flu was a disaster waiting to happen.”
The problem is that the virus has been evolving rapidly in a microscopic arms-race against the hog immune system.
When pig mortality started affecting profits after 1998, the meat industry went into vaccinating overdrive. But inoculation hasn’t stemmed the flow of new flu strains, writes Peter Aldhous in a separate New Scientist article.
The virus has been mutating and evolving faster than the pharmaceutical industry, or at least the US Department of Agriculture, has been able to keep up.
“We only chased this virus with vaccine rather than confront it,” said Rodney Baker who was formerly a vet for major US pork producer Premium Standard Farms.
While small drug companies would compound batches of vaccine for specific strains affecting a particular herd of pigs, it takes months or years for those vaccines to get USDA approval for the mass market. By then the dominant virus strain would have already evolved to beat the vaccine.
“Under some circumstances, the vaccines may even have made the disease worse,” Aldhous writes.
In one test on the effectiveness of the vaccines Baker inoculated 20,000 pigs with a mass-produced vaccine and left another 20,000 untouched. Twice as many pigs died in the vaccinated group than in the control. In theory a vaccine can make a virus more potent if there is a slight difference between the vaccine strain and a new mutation.
But stopping the vaccinations is not an option because the viruses now circulating in North American pigs would, if left unchecked, keep spreading further.
New Scientist is careful to point out that pig vaccination programs cannot be blamed for the evolution of flu strains. Pig reassortants are notoriously promiscuous, Aldhous explains, readily swapping surface proteins to slip past immune systems. “Even if no vaccines had been used, natural pig immunity would probably have been enough to drive the emergence of new variants,” he writes.
More effective, genetically modified vaccines that stop virus strains from mutating may become available in the future. But research is expensive and the pork industry is under pressure from rising feed prices and low supermarket prices.
So, given the choice between bargain pork chops and lowering the risk of a global flu pandemic, what would you do?
(Photo of pig farm from magnusgas.com)
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