Antibiotic resistance is often framed as a medical problem, but it is equally an agricultural one. In many countries, more antibiotics are given to healthy livestock — to promote growth and prevent disease in crowded conditions — than to sick humans. Resistant bacteria that evolve on farms do not stay there: they travel through meat, water and farm workers into the wider community. Several countries that banned growth-promoting antibiotic use in animals have seen resistance rates in human infections fall, evidence that the farm and the clinic are a single connected ecosystem rather than separate worlds.