The Rising Plague, a book by Brad Spellberg, chief medical officer of the Los Angeles County—University of Southern California Medical Center, opens with eight chilling words:

“I’m out of antibiotics. She’s going to die.”

The quote is from a real doctor at UCLA-Harbor Medical Center, who was treating a real patient—a 20-something Spellberg calls “B.” B had leukemia, and she developed an infection that built up resistance to the hospital’s most powerful antibiotics even as she was being pumped full of them. She died the day after Spellberg told her husband the hospital had nothing left to try.

In the book, Spellberg describes the case as happening “several years ago.” The book was published in 2009.

Antibiotic resistance may make cases like B's much more common in the future. One of the biggest culprits is the widespread use of antibiotics in livestock. Industrial farms feed animals low doses of the drugs in order to promote growth and ward off infections within densely packed herds. From there, natural selection does its job: The bacteria that can overpower the drugs survive and multiply, and they make their way out into the environment through water, urine, and feces. In the U.S., 80 percent of antibiotics are used in animals, though the industry is moving away from the practice.

A new study published in the Proceedings of the National Academy of Sciences forecasts the geography of antibiotic overuse in the future. According to the study authors, the next big threat will come from middle-income countries like Brazil, Russia, India, and China, where a burgeoning consumer class is starting to prefer more meat in their diets, and where large-scale farms will try to meet this demand as cheaply as they can.

Antibiotic Consumption in Chicken and Pigs

Antibiotic consumption in chickens (top) and pigs (bottom) in 2010. Purple indicates new areas where antimicrobial consumption will exceed 30 kg per 10 km2 by 2030. (PNAS)

The study authors estimate that between 2010 and 2030, the global consumption of antibiotics will increase by 67 percent, with about a third of that increase coming from changing livestock practices in fast-developing countries. China, for instance, already leads the world in antibiotic use in livestock.

The increase will largely be driven by chicken and pork, rather than cattle. Chicken and pigs are easier to raise quickly in tight spaces, whereas cattle herds take a while to build up, explained Timothy Robinson, principal scientist at the International Livestock Research Institute and an author of the study.

It’s particularly devastating that developing countries will use the most antibiotics in livestock because they also shoulder a disproportionate disease burden. For example, the authors write, “India has no regulatory provisions for the use of antimicrobials in cattle, chicken, and pigs raised for domestic consumption,” but approximately 95 percent “of adults in India carry bacteria resistant to β-lactam antimicrobials.”

These are also the nations where restrictions on antibiotic use might be hardest to implement.

“In Europe, we have fairly strict legislation on antimicrobial use,” Robinson said. “In the States, things are a bit looser. In India and China and Russia, it's one thing producing the legislation and it's another thing enforcing it.”

All of this made me wonder how much good it does to buy antibiotic-free meat in the U.S., which, unlike the EU, hasn’t outlawed the use of antibiotics in livestock as a growth promoter.

The answer is: It depends. Chicken raised without antibiotics might have a lower chance of harboring resistant pathogens like Campylobacter and Salmonella, says Ramanan Laxminarayan, director of the Center for Disease Dynamics, Economics and Policy.

Still, choosing antibiotic-free chicken is still a little bit like buying a Prius or recycling: It could help on a wide scale, but only if most people do it. Even if some people are chowing down on Whole Foods poultry, superbugs from chicken farms that do use antibiotics could still make their way to humans through the water supply and other means. According to Laxminarayan, this is how most resistance genes get to humans, rather than through the direct consumption of animals raised on antibiotics.

“Antimicrobial resistance is a tragedy of the commons, but with more direct individual effect than climate change,” said Thomas Van Boeckel, an ecologist at Princeton University and the study's lead author. “By playing your part you do reduce your risk of infection. Although not completely.”

In order to preserve antibiotic effectiveness entirely, he added, “we need to rethink how we raise livestock.”