Getting sick today is a chore. Finding out what’s wrong means scheduling an appointment, driving to the doctor’s office, filling out forms, waiting, and answering questions while being swabbed and poked. Then you wait for test results, pick up your prescriptions, and schedule more appointments with specialists. The nuisance of seeking care is quickly becoming a crisis around the world, as declining birth rates and aging populations put a crushing burden on national healthcare systems.

Soon, governments, insurers, and taxpayers around the world will be forced to confront a complicated and inefficient system that focuses too much on managing disease when it arrives and not enough on preventing people from getting sick. A critical step in reforming the system will be making visits to a doctor’s office a last resort rather than a first step.

This shift will require all kinds of structural, legal, and financial changes, but innovations in computing, communications, biology, nanotechnology, and robotics will ease the way. The Web is already allowing patients quick access to quality health information once dispensed only by white coats. Soon, patients will access customized health plans online. Diagnosing and treating many everyday conditions will be as simple as depositing a drop of blood in a machine and, within moments, having the computer tell you what you have and how to get rid of it.

Doctors won’t be obsolete, of course. In fact, general practitioners will be more important than ever, but they’ll spend more time assessing options for preventive action and less time shepherding patients through their offices. Doctors will increasingly rely on highly personalized treatments—such as new drugs targeted specifically to personal needs, or even nanomachines that attack bad...