A small group of people with a common goal: in American mythology, this is where famous rock bands and big businesses often begin. It is where in fact Partners In Health got started 25 years ago—with five American friends who were appalled by the great sickness of poverty in the world and who dreamed of seeing it cured. Needless to say, Partners In Health (PIH) has not succeeded yet. But it has made progress.

In its earliest days, PIH’s infrastructure was a two-room office over a seafood restaurant in Cambridge, Mass., and a one-doctor clinic in a squatter settlement in the Central Plateau of Haiti—in those days a wilderness of extreme poverty and disease. PIH was a grand idea then, and it is a grand idea today, but with a lot more behind it: some 14,000 employees who manage dozens of hospitals and clinics and have built and still are building schools and water and sanitation systems and houses for the very poor. PIH is doing that work in eastern Europe, Asia, South America, Africa, and of course in Haiti, the heartland of PIH, where it is struggling now to stanch a dreadful cholera epidemic and to lay durable foundations for the country’s post-earthquake reconstruction.

In all, PIH directly serves about 2.5 million of the world’s poorest people. It directly serves about 1.3 million in Haiti, in 12 different hospitals and clinics, providing medical care on the scale of a couple of big Boston teaching hospitals but at vastly smaller cost. Some aid organizations are notoriously self-serving, using large portions of the money they receive for their own administration and comfort. PIH spends only 7 percent of the money it receives from private donors on administration and fundraising.

It is mainly because it has grown in service that PIH has also grown in influence. PIH played an important part in the international debates about whether AIDS could and should be treated in places like Haiti and sub-Saharan Africa, debates that have largely been resolved in favor of treatment. But PIH’s role had less to do with talk than with its own AIDS treatment program in Haiti, which provided vivid, incontrovertible proof that the disease could be treated successfully in a deeply impoverished setting.

PIH did much the same thing with drug-resistant tuberculosis. They proved that controlling this disease was possible by devising and administering effective treatment in a peri-urban slum in Peru. They also played the central role in driving down the prices of the necessary drugs. Since then more than 100 countries have adopted PIH’s prescriptions for dealing with that dread and still widespread disease. Last summer PIH opened the first comprehensive cancer treatment center in all of rural East Africa. In this and many other ways, the organization continues to defy assumptions that many illnesses can’t be treated in the world’s impoverished places.

The scope of PIH’s work is international, and the heart of it is local. All its work relies on well-trained and salaried community health workers, more than 8,000 of them now, who serve patients in their own communities—“accompanying” those patients, in PIH parlance. This is the essence of PIH’s grand strategy, to address particular problems in particular places, and to learn how solutions in one place can be tailored to another. Part of this strategy lies in making projects indigenous. All too often aid organizations fail to do this, virtually guaranteeing that their projects won’t last, let alone flourish and spread. By contrast, all but a tiny fraction of PIH employees come from the countries and communities that are being served.

Waking up in the morning to news of the world, one can justly feel that violence and chaos are fully in charge. Just personally, I find it more than reassuring at such moments to know that there are some effective counterforces, some people out there trying to offer cures for the world’s great sicknesses. Nothing but hope suggests that these counterforces will prevail. But some basis for hope is far better than none. PIH’s vivid proofs of what can be accomplished in the face of poverty and disease is such a basis. It is, I feel, one of PIH’s most important gifts to the world.

Tracy Kidder, a longtime PIH supporter, is the author of Mountains Beyond Mountains: The Quest of Dr. Paul Farmer, a Man Who Would Cure the World, and Strength in What Remains, among other books. His latest is Good Prose: The Art of Nonfiction.