Science Talk

How You Gonna Keep Flu Down on the Farm?: Pig Farms and Public Health

Journalist Helen Branswell discusses her January Scientific American article, "Flu Factories," about the attempts to monitor new strains of flu that can originate on pig farms and the difficulties of balancing economic and public health constituencies

Journalist Helen Branswell discusses her January Scientific American article, "Flu Factories," about the attempts to monitor new strains of flu that can originate on pig farms and the difficulties of balancing economic and public health constituencies. Web sites related to this episode include

Podcast Transcription

Steve:          Welcome to the special Web Extra edition of Science Talk, the podcast of Scientific American, posted on December 22nd. I'm Steve Mirsky. On this episode…

Branswell:         There were people who knew what was circulated in pigs but they were, generally speaking, researchers who worked for animal health labs. That information didn't, generally speaking, flow down to the Centers for Disease Control in Atlanta where people who were concerned about human health and warning to watch what was going on in pigs so they could be on the lookout for changes there.

Steve:          That's Helen Branswell. She is a medical reporter for the Canadian press and one of the world's most knowledgeable journalists about flu. Her article in the January issue of Scientific American magazine is called "Flu Factories" and explores the uneasy relationship between pig farms, where new flu strains can originate, and the public health community. The article is also available on our Web site. She is currently a Nieman Fellow for Global Health Reporting at Harvard University. I called her in Cambridge, Massachusetts.

Steve:          Let's start with a brief primer on the whole issue of flu and how human beings, pigs and birds are all related in the whole flu business.

Branswell:         Well, [as] people will know, there are human flu viruses that circulate amongst us, generally speaking in the winter months, and there are a few of them, but they're, kind of, finite in number at any one time. Right now we've got H3N2 viruses, we have got the pandemic H1N1 virus that emerged in 2009, and we have influenza B viruses. At any time in the winter those viruses are circulating, some years more than others, and can make us sick. In birds and pigs however, there are different assortments of viruses, and those viruses can sort of act as a reservoir—a gene reservoir, if you will—for viruses that could eventually make their way to human beings. All flu viruses are derived from birds, water fowl in particular; ducks are really key in that. And from birds, these viruses can make their way into other animals. We've seen in the last few years, discoveries of flu viruses in anteaters and opossums and skunks and raccoons—all sorts of animals that people didn't know before are actually susceptible to flu viruses. Pigs in particular are really susceptible to flu viruses, and the reason pigs are important is because they sort of form a bridge between birds and people. They have contact with birds. If they are free range, they have contact with birds or bird droppings and can become infected with bird viruses, and then they have contact with people. And so if a pig is sneezing with flu, the person who is feeding the pig may come down with a flu virus that was passed to him from a pig.

Steve:          And another important thing is anteaters are not in the tens of thousands on a single farm in North Carolina.

Branswell:         Precisely, and likewise we don't have much contact with skunks, you know—we try not to let a skunk sneeze on us. So really the important animals in this equation are the ones that can bring the novel viruses—the viruses that humans haven't had any experience with—from the natural reservoir to the human population.

Steve:          So we can look at any individual pig as a test tube or petri dish in which a lot of genes from different sources may have an opportunity to mix together.

Branswell:         Yeah, that's correct because one thing that's important here is that bird viruses don't pass often directly to people, probably because we don't have that much close contact with birds but as well the receptors in our respiratory tract aren't the type of receptors that those viruses latch on to well. Pigs, on the other hand, can catch both bird influenzas and human influenza viruses; they have both kinds of receptors. So, that makes them this perfect—[you] use[d] the the term, petri dish; some people call them a mixing bowl. They can catch both kinds of flus, and if they do concurrently, those flus can mix and swap viruses and create a whole new entity.

Steve:          So let's throw another metaphor into the fray here, and in your article, you say that pigs can be looked at as the Achilles' heel of global flu surveillance, and that's really the crux of your piece.

Branswell:         Right. Over the last five or 10 years, the world has been paying a lot of attention to bird flus because of the very dangerous H5N1 virus—people know it as bird flu—that has been circulating in Asia and Egypt still. That virus kills about, it jumps occasionally into people, and when it does it kills about 60 or 66 percent of the people who get infected with it.

Steve:          Which is gigantic.

Branswell:         Yeah, that's puts it in the realm of, well, science fiction almost. But fortunately for humans, it's not something that [is] transmitted to humans very often.

Steve:          I mean that's worse than bubonic plague or smallpox.

Branswell:         Yeah, I was going to use some of the hemorrhagic fevers but I am reluctant to go there because at this point there have been cases seen where it passed from birds to people and, you know, there have been a few cases where it seems like it probably passed from one person to a second person or maybe a third person. But it has not got the capacity to spread efficiently from person to person to person, which would be what would be needed for it to become a real threat to humanity, and we hope that that won't happen.

Steve:          And one of the keys to that not happening is surveillance, and that brings us back to the pigs.

Branswell:         Right, exactly. So people have been doing a lot of surveillance because of that virus and watching for it in bird population. But as we said before pigs can be infected with [both] human and bird viruses, so you really want to be watching pigs, because they can be the source of new viruses coming to humankind. I mean it seems pretty obvious that the pandemic virus of 2009, the H1N1 virus, came from pig populations somewhere in the Americas and that could happen again.

Steve:          And in 2009 the effect in the United States was not particularly severe, and so a lot of people thought that we may've overreacted.

Branswell:         Yeah, I know that a lot of people thought that pandemic was, sort of, much of the above nothing. From where I sit it was a very lucky break. You know, it turned out to be a virus that was new enough to make a portion of the population sick but wasn't entirely novel. People who were, sort of, over 60 had encountered viruses like it in their past, and so they weren't all that susceptible. And when you think about flu and who normally dies from flu, it's generally the elderly. We didn't see a kind of that with this pandemic which was very; it was very effective at making younger people sick and some people very, very sick. You know people in their late 30s and 40s, and particularly, especially if they had any underlying health problems. Some of them became enormously sick and we also saw people who had no previous health problems who ended up on respirators or even dying. So, if a virus that we thought of as not terribly bad could do this, you have to realize that if something worse came down the pipe, we could have a real problem. I mean, in places like the United States and Canada some of the hospitals, they didn't get to the point where they were completely overrun, but they were certainly severely taxed in their ICUs. I mean, people were moving around at ECMO equipment and ventilators because, you know, hospitals got stretched in that regard. If something that wasn't terribly bad stretched the system, you know, you have to think about what would happen if a worse bug came along and more people got severely ill.

Steve:          Absolutely. And now let's talk about, there is a conflict between the business community and the public health community, and should I have more sympathy for the pig farmer who wants to keep his, the issue is they want to keep their data secret. They don't want to share their surveillance data about the incidence of flu on the farm with the public health authorities.

Branswell:         I think that overstates it a little bit. People on both sides, the animal health side and the human health side, have been working together for the past couple of years trying to come up with a better system, and they have come up with something that could probably be termed as a compromise which does let more information flow from the animal health people to the public health people who have to be concerned about all of us. So, some change is being effected. So, in the past what happened was there were people who knew what was circulating in pigs, but they were generally speaking, researchers who worked for animal health labs in the United States. Some of those labs are located at big universities and big pig producing states. That information didn't, generally speaking, flow down to the Centers for Disease Control in Atlanta or people who were concerned about human health and warning to watch what was going on in pigs so they could be on the lookout for changes there. A couple of years ago, the US Department of Agriculture and the CDC started talking about a system that would allow more information to flow from the animal health side to the human side, and they put in place a system that lets that happen, but it's got a lot of safeguards built in for the producers. And so, for instance, viruses that are submitted into this new system that lets them flow to the human health folk, they are all "anonymized." So, the CDC could see a virus that was unusual or needed to be followed up on, and they would know perhaps that it came from Iowa or North Carolina, but they wouldn't know what part of that state or what farm in that state—that information wouldn't be available for them.

Steve:          What is the pork industry actually trying to protect by keeping that information, you know, a little sketchy?

Branswell:         The industry, I mean, if you think back to what happened in the spring of 2009 when that new virus emerged and was identified as a swine flu virus, and what happened as a consequence—to sell pork, prices went to the floor, people didn't want to buy pork. They [had the] mistaken idea that you could catch the flu from eating pork products, which is not true, but it really hurt the industry, and they don't want that to happen again. I don't know if you remember this, but by the end of May of 2009, a farm in Alberta, Canada, it's pigs were found to be infected with the pandemic virus, and it's the first time in the pandemic that that was seem to have happened. That farmer couldn't sell his pigs, even after his pigs [had] completely recovered. No one would buy those pigs, and as a consequence he had to put them down, because he couldn't afford to feed them any longer. He almost lost his farm. Pig farmers know that and they don't, you know, they remember that story. It was a real cautionary tale for them, and they're very concerned that the industry doesn't take that kind of hit again for something that they don't actually think is that big a deal.

Steve:          And yet it's a small risk but the consequences are major. Should a pandemic emerge, then you have a much more severe economic situation that spreads way beyond the pig farms.

Branswell:         That's true but, I mean, if you talk to them, or people representing the industry, they'll say to you, "Yes we know that's true, but in the course of a year or even a day around the world, untold numbers of people come in contact with pigs and pandemic viruses don't emerge every time that happens." And in fact they hardly ever emerge. The 2009 pandemic was the first one in 41 years. So they're not certain how much of a public relations hit they're meant to take to prevent something that, you know, may not happen for another couple of decades.

Steve:          So, is the current situation a reasonable one? Have we balanced the public's interest with the interest of the pork industry successfully?

Branswell:         I am not sure if that's for me to say. I think I feel more comfortable saying that I know that on the human health side, people who are involved in this hope to be able to push this to further down the road. They see this as a compromise and maybe a first step, but they certainly don't think that they are getting as much information and as in as timely a manner as they would like, and they certainly would like to see improvements made to the system.

Steve:          What kind of specifics would they prefer?

Branswell:         I think that the anonymity poses a problem in some regards because if they saw something that really need to be followed up, they are not clear that they would be able to get the information to know where to look in the state, for example. One of the people I spoke to, Dr. Nancy Cox, who heads the influenza division at the Centers for Disease Control in Nevada, was saying, for instance, that when they see something and in the past or at least when they've seen something, by the time they try to follow up the pigs, the herd that was involved has already been slaughtered, so it's really almost impossible for them to put together what happened. I think that people would just like more information, more quickly and to try to prevent the situation that happened in 2009 where by the time human health was able to stop what was going on, the horse was out of the barn.

Steve:          Well the pig…

Branswell:         Yeah, that, too.

Steve:          Helen Branswell's article "Flu Factories" is in the current issue, the January issue of Scientific American, and also available on our Web site, I created a short URL for it: just go to for a preview.

A new Scientific American iPad app is out; it's called "Origins and Endings Scientific American" and it's a chock full of fascinating articles from our two most-recent single topic issues. There's also audio, video and interactive content. So check it out, iPad users out there, and don't forget our other app "Scientific American Advances," for your general browsing needs for the iPad, the iPhone and the iTouch.

Well that's it for this special Web Extra. We'll be back with another Web Extra later this week as well as the second part of our look at health care from unusual perspectives—this time from the nurses' station. For Science Talk, the podcast of Scientific American, I am Steve Mirsky. Thanks for clicking on us.

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