When antibiotics began to be used widely in the 1940s, they transformed medicine almost overnight. Diseases that had killed millions of people for centuries - pneumonia, tuberculosis, meningitis, wound infections - suddenly became treatable in a matter of days. Within a generation, many doctors assumed that serious bacterial illness was essentially a solved problem. That optimism now looks badly misplaced. Bacteria have evolved resistance to one antibiotic after another, and the World Health Organization has described the problem as one of the most serious long-term threats to global health.
The basic cause of resistance is an ordinary evolutionary process. Whenever a population of bacteria is exposed to an antibiotic, any individual cells that happen to carry mutations making them resistant are more likely to survive and reproduce. Over time, the resistant bacteria come to dominate, and the drug loses its effectiveness. This process has been observed in laboratories for decades. What has accelerated it outside the laboratory is the way antibiotics are used in hospitals, clinics and, above all, in agriculture.
In many countries, antibiotics are routinely added to animal feed to promote growth, even when the animals are not ill. Doctors in some regions prescribe them for viral infections, against which they have no effect at all. Patients often stop taking their course of antibiotics as soon as they feel better, allowing partially resistant bacteria to survive. Each of these practices provides countless opportunities for resistance to develop and spread.
The response must therefore combine scientific and social measures. New classes of antibiotic are being sought, though the rate of discovery is far slower than in earlier decades. At the same time, governments and medical bodies are working to restrict unnecessary use, improve infection control in hospitals and limit antibiotic use on farms. Progress is uneven, but the direction is clear: if antibiotics are to remain useful for the next generation, the reckless use of the past cannot continue.