Statistics hog-tie pig farming to H1N1 cases

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      As hospitals brace for the coming flu season and a possible new surge of H1N1 cases, international data on the flu pandemic shows it has hit Canada worse than almost any other country.

      And a close look at the data suggests that a key factor may be something that health authorities have largely overlooked: hog farming.

      Canada had the sixth-highest number of H1N1 cases per capita and the fifth-highest per capita rate of H1N1 deaths of all 134 countries and dependencies that had reported flu cases to the World Health Organization as of July 6. (That’s the last date for reliable international comparisons, because the WHO advised countries in early July to stop reporting data on individual H1N1 cases.)

      Canada’s H1N1 rate was almost 15 times the global average—23.7 lab-confirmed cases per 100,000 people, compared to an international average of 1.6 cases per 100,000, according to the WHO data. Canada’s per capita rate was double that of the U.S. and 2.5 times that of Mexico, where the pandemic is thought to have started.

      Canada’s H1N1 death rate was 10 times the international average: 7.4 deaths per 10 million people, versus 0.7 globally.

      It’s not clear why Canadian H1N1 rates are so high. One possibility is that Canadian medical authorities have simply sent more cases to labs for testing. But the data also suggests another possible factor: Canada’s high concentration of hog farms.

      It just so happens that Canada has the world’s eighth-highest number of pigs per capita—almost 15 million pigs, or about one for every two Canadians. And an analysis of international flu data shows that H1N1 rates have strong correlations with hog farming.

      In Mexico, where it probably all started, there was a moderate, statistically significant 46-percent correlation between confirmed per capita H1N1 cases in all of the country’s 32 states and its federal district and the number of pigs per capita in those states. That’s according to the data as of July 2, the date the Pan American Health Organization stopped publishing the breakdown of flu cases within countries of the Americas.

      (Correlation measures the strength of the relationship between two groups of data. A correlation of 30 to 50 percent is generally considered to be moderate, 50 to 70 percent is strong, while 70 percent or higher is very strong.)

      Yucatán was the Mexican state with the highest rate of H1N1 cases per capita: 92 per 100,000 people. It’s also one of the country’s hog-farming hubs, with the most pigs per capita of any state, more than one for every two people.

      Argentina had the world’s highest per capita death rate from H1N1, with 15 deaths per 10 million people, or 20 times the world average of 0.7 deaths. In Argentina’s 24 provinces and its capital district, there was a 70-percent correlation between the per capita death rate and the ratio of pigs to people.

      The Argentinean province that had the highest death rate was Santa Fe, with 130 H1N1 deaths per 10 million people. Santa Fe also happens to have Argentina’s highest ratio of pigs to people.

      And those countries aren’t the only ones where there’s apparently a relationship between the pandemic and hog farming. Among the 39 countries and dependencies in the Americas that had reported H1N1 cases as of July 6, there was a 51-percent correlation between H1N1 cases per capita and the number of pigs per capita.

      Globally, the 20 countries with the most pigs per capita had a per-capita H1N1 rate of 5.5 per 100,000—more than 3.3 times the international average of 1.6 cases. As well, their per capita death rate from H1N1 was 2.5 per 10 million, or more than triple the international average of 0.7.

      “This is a very serious concern,” said Bob Martin, who headed the Washington, D.C.–based Pew Commission on Industrial Farm Animal Production, when told about the Georgia Straight’s data analysis. “It’s just another step in showing what serious impacts these large-scale swine operations can have.”

      Martin’s commission released a study last year that said workers in large farms, and their neighbours, have high rates of asthma and other respiratory illnesses due to manure runoff and emissions like ammonia and fine-particle pollution. Respiratory illness makes people more vulnerable to H1N1, he said.

      A high portion of H1N1 hospitalizations and deaths have occurred among people with an additional medical condition like asthma or a compromised immune system.

      In an initial story in July, the Straight reported that strong correlations exist between per capita H1N1 rates and the number of pigs per person within B.C.’s five health regions and in each of Canada’s provinces.

      As of July 8, Manitoba, the country’s hog-farming capital, with 2.4 pigs per person, had three times as many H1N1 hospitalizations per capita as the Canadian average and 3.7 times as many deaths per capita.

      The international data puts the high Manitoba numbers into even starker perspective. Manitoba’s per-capita H1N1 rate, 65 per 100,000 people, was 40 times higher the international average and far worse than that of the country with the highest rate in the world, Chile, which had 44 cases per 100,000.

      Manitoba’s death rate—41 per 10 million people—was 60 times the global average and nearly three times that of Argentina, the worst-hit country in the world in terms of deaths.

      So far, Canadian public-health officials have said the flu pandemic is spreading mostly randomly, though they acknowledge it has hit some vulnerable populations harder, especially those with respiratory problems, aboriginal people, and pregnant women. Most scientists believe H1N1 originated on a huge Mexican factory pig farm, then spread between people around the world.

      In Canadian aboriginal communities, H1N1 is thought to be worse because of poor health care and overcrowding. Indeed, the data confirms that Native people have been hit harder and need extra resources to deal with H1N1. The per capita number of H1N1 cases in each province had a very strong 87-percent correlation with the per capita number of aboriginal people.

      That’s even higher than the 77-percent correlation between per capita H1N1 cases and the per capita number of pigs in the 10 provinces.

      However, when it comes to more serious H1N1 cases that involved hospitalization and death, the correlations were stronger for hog farming. There was a 44-percent correlation between per capita H1N1 hospitalization rates and the number of aboriginal people per capita in each province, compared to a 72-percent correlation between hospitalization rates and the per capita number of pigs in each province.

      H1N1 deaths per capita had an 82-percent correlation with the percentage of aboriginal people in each province, but had an even stronger 89-percent correlation with the number of pigs per capita.

      “I hope the World Health Organization will start looking at the same data you’re looking at,” the Pew Commission’s Martin said in a phone interview.




      Aug 27, 2009 at 8:59am

      Maybe this just shows how many hog farms there are in urban areas but 89% is a strong correlation.


      Aug 28, 2009 at 5:30am

      I wonder: in the July story, it said that Quebec is the Canadian province that has the highest number of pigs, and in this story, it says that Manitoba is the pig capital of Canada. I guess the difference is Manitoba is the highest number of pigs per person?


      Aug 28, 2009 at 6:13am

      Wow, what a lousy, circumstantial case you have presented here. Canada had more flu. Canada has pigs. Therefore, the pigs are causing the flu. Yeah, good reasoning there. Maybe it's the wood...Canada also has a big wood industry. Lots of trees, lots of flu. Sounds reasonable to me. Blame the trees.


      Aug 28, 2009 at 8:59am

      The Pew commission is anti modern farming and any statistic that they come up with are tainted in the their direction. I would like to know who provided these statistics because they look very biased to me, plus come on folks there have been less than 2,000 DEATHS AROUND THE WORLD. I don't mean to trivialize anyone passing however there are probably more people dying from ingrown toenails around the world that what has been caused from H1N1. Lets stop creating fear through the public, this is just a way to keep news agencies going!


      Aug 28, 2009 at 10:26am

      Excellent compelling analysis. Why isn't anyone else looking into this?

      Martin Dunphy

      Aug 28, 2009 at 12:05pm


      None of the statistics in the story came from the Pew Commission. They are all the result of research done by the author of the article.
      And what's wrong with news agencies?


      Aug 28, 2009 at 1:01pm

      If H1N1 stats and pig stats correlations are so circumstantial, why does the Agricultural Minister of Saskatchewan want us to stop calling it the swine flu, and why did the WHO announced on the 30th of April that it would drop the name "swine flu", and why does the National Pork Producers Council email the media so the name "swine flu" be dropped? We know very well we can't get swine flu from eating the meat, so why are they so nervous?

      On the 30th of April, the media reported that the WHO changed the name after being pressured from the agricultural industry. Now I can't find the articles reporting that. Isn't that strange?


      Aug 29, 2009 at 5:44am

      Got it! Dated April 30th, 2009, part of article by Reuters: "The World Health Organization (WHO), bowing to pressure from meat industry producers and concerned governments, said on Thursday it would refer to a deadly new virus strain as influenza A (H1N1), not swine flu." and further down the text: "While it contains mostly swine flu genetic sequences, it also contains small amounts of human and bird flu virus genetic material."

      I think human health decisions should not be swerved by the meat industry producers. There are so many reasons to change CAFOs methods, the swine flu is one more to be added on the pile.


      Aug 31, 2009 at 9:07am

      Hi Johanne,

      Thanks for your comment. That's right - Quebec has the most pigs (over 4 million according to the latest census data), but Manitoba has by far the most pigs per capita (2.4 per person, compared to 0.5 in Quebec).



      Sep 2, 2009 at 6:38pm

      Thank you for a a great and compelling article.
      I simply can not comprehend why people are still consuming pigs knowing they come from filthy, cruel and stressful living conditions. Not to mention viruses connected to factory farming!