May 3, 2009
What You Should Know about Swine Flu
Q&A with Dr. Michael Greger
Michael Greger, M.D., is the director of public health and animal agriculture for The Humane Society of the United States. His book Bird Flu: A Virus of Our Own Hatching, which is available full-text online, explores the risk of avian influenza, which has many parallels with the current swine flu outbreak. He answers common questions about the burgeoning pandemic.
Is it still even called "swine" flu?
To protect pork exports and deter countries from indiscriminately killing pigs, many have dropped use of the term "swine." The U.S. Centers for Disease Control and Prevention has decided instead to call it "swine-origin" influenza now, which is accurate, but people have been raising pigs and chickens in their back yards for thousands of years before the triple hybrid mutant ancestor of this virus was first detected on U.S. factory farms. "Factory farm flu" might therefore be more accurate.
If I properly handle and fully cook pork, is it safe?
From an influenza standpoint, pork is probably safe, but how that pork was produced can be anything but. When thousands of pigs are overcrowded into cramped stalls and pens inside massive, unsanitary, warehouse-like sheds, it's a veritable breeding ground for disease. As the former executive director of the Pew Commission on Industrial Animal Farm Production described, "Industrial farms are super-incubators for viruses."
Where did swine flu come from?
The genetic fingerprint of the virus was just published, and the main ancestor of this deadly virus is a triple hybrid mutant first found on factory farms in the United States in 1998. The H1N1 swine flu virus has been described as "the product of intensive farming."
What are the conditions on factory farms that contribute to emergence of these diseases?
Factory farms can be considered viral breeding grounds for many reasons:
- The sheer number of confined animals: With so many animals—stressed, deprived and suffering from poor welfare—overcrowded in today's factory farms, a pathogen can run rampant and mutate among so many confined "hosts." As Johns Hopkins School of Public Health Professor Ellen Silbergeld put it: "Instead of a virus only having one spin of the roulette wheel, it has thousands and thousands of spins, for no extra cost. It drives the evolution of new diseases."
- The unnatural stocking density: Swine flu is transmitted like human flu, via infected nasal secretions and respiratory droplets. So, when pigs are intensively confined on factory farms, the large viral loads considered necessary for the emergence of rare flu mutants can rapidly transfer from animal to animal.
- The stress crippling their immune systems: Breeding sows confined in gestation crates can't even turn around and their health can suffer immensely. According to veterinary scientists, crowding more pigs per pen "allows more opportunities for direct nose-to-nose contact or for aerosol spread of the [swine flu] virus between penmates. Furthermore, a large number of pigs per pen creates physiological stress, which in turn can alter the immune system and predispose pigs to infection.
- The lack of adequate fresh air: The dankness helps keep the virus alive.
- The decaying fecal waste: The millions of gallons of excrement produced by a typical operation decompose and release ammonia, burning the pigs' respiratory tracts, which may predispose them to respiratory infection in the first place.
- The lack of adequate sunlight: In factory farms, there may be no sunlight. The UV rays in sunlight are quite effective in destroying the influenza virus. Thirty minutes in direct sunlight completely inactivates the flu virus, but it can last for days in the shade, and weeks in moist manure.
- Pharmacological crutches: Just as the U.S. pork industry jeopardizes the public through the mass feeding of human antibiotics to pigs to offset the effects of intensive confinement, the industry vaccinates its herds for swine flu. This minimizes the virus’ impact on production, but may not significantly reduce viral shedding. Instead, it immunologically pressures the virus to mutate by acquiring novel human virus surface proteins, as has happened in Eurasia and north America, which may increase its pandemic potential.
- Preponderance of disease-carrying rodents, flies, and other vectors: A 2006 study found evidence that flies may be able to pick up flu viruses from factory farms and carry them for miles.
Put all of these factors together and what you get is a "perfect storm" environment for the emergence and spread of new "superstrains" of influenza, which long-distance live animal transport can then rapidly spread across the country.
Have there been other diseases related to factory farming?
Swine flu is not the only deadly human disease traced to factory farming practices. The meat industry took natural herbivores, such as cows and sheep, and turned them into cannibals by feeding them slaughter plant waste, blood and manure. Then, people were fed downed animals—those too sick even to stand or walk—and, as a result, people have died because of mad cow disease.
In 2005, China experienced the world's largest and deadliest outbreak of an emerging pig pathogen called Strep suis, causing meningitis and deafness in people handling infected pork products. The U.S. Department of Agriculture blamed "[s]tress due to poor housing conditions, such as crowding and inadequate ventilation..." and the World Health Organization similarly blamed "'intensive' conditions that can cause stress and subsequent immune suppression."
Pig factories in Malaysia birthed one of the deadliest of human pathogens, the Nipah virus, a contagious respiratory disease causing relapsing brain infections and killing 40% of people infected. Its emergence was again blamed on factory farms.
The pork industry in the United States feeds pigs millions of pounds of human antibiotics every year just to promote growth and prevent disease in such a stressful, unhygienic environment, and now there are multidrug-resistant bacteria and we as physicians are running out of good antibiotic options. A study published last year found that half of pigs tested in Iowa and Illinois were positive for MRSA (methicillin-resistant Staphylococcus aureus), which now kills more people than AIDS in the United States. As the United Kingdom's chief medical officer put it, "every inappropriate or unnecessary use in animals or agriculture is potentially a death warrant for a future patient."
How do other public health scientists feel about these factory farms?
The largest association of public health professionals in the world, the American Public Health Association, called for a moratorium on factory farms more than five years ago.
In 2005, the United Nations said, "Governments, local authorities, and international agencies need to take a greatly increased role in combating the role of factory farming," which, combined with live animal markets, "provide ideal conditions for the [influenza] virus to spread and mutate into a more dangerous form." These factory farms can be thought of as the original incubators of dangerous strains of the flu.
Just last year, the Pew Commission on Industrial Farm Animal Production released its final report after a two-and-one-half year investigation. Commissioners included a former U.S. Secretary of Agriculture, a former Assistant Surgeon General and the Dean of the University of Iowa College of Public Health, and was chaired by a former Kansas Governor. The Commission concluded in no uncertain terms that intensively confining pigs in veal crate-like metal stalls where they can't even turn around poses "unacceptable" public health risks.
What needs to happen to decrease our risk of future swine flu pandemics?
The industry needs to immediately move towards a carcass-only trade. Long-distance live animal transport has been implicated in the rapid spread of swine influenza viruses throughout North America.
We also need to start giving these animals more breathing room. One study showed that measures as simple as providing straw for pigs so they don't have the immunosuppressive stress of living on bare concrete their whole lives can significantly cut down on swine flu transmission rates. In the long run, though, we need to follow the Pew Commission's recommendations to abolish extreme confinement practices like gestation crates, as they're already doing in Europe, and to follow the advice of the American Public Health Association and declare no more factory farms.
How bad do you think this is going to get?
The goal is to be prepared, not scared. There are pandemics and then there are pandemics. We must remember that the last two pandemics—in 1957 and 1968—were relatively mild, only killing about a million people each. If you're 52 years old, you've already lived through two pandemics, and odds are you'll almost certainly live through the next.
Nearly everything you need to know to survive a pandemic you likely learned in kindergarten, such as proper hand washing and basic respiratory hygiene. Also, getting up to speed on social distancing, appropriate stockpiling of essential supplies, taking care of flu victims, and the proper use of alcohol-based hand sanitizers and masks/respirators may be helpful should the current swine flu virus evolve into a more serious threat.