The campaign to help the world’s poor may not be awash in money. But it’s not the beggar it used to be.

The nation’s richest and second-richest men, Bill Gates and Warren Buffett, have now pledged much of their fortunes to the cause of global health. The United States and other industrialized countries spend billions each year on AIDS treatment and prevention in the developing world. Several pharmaceutical companies are supplying gratis vast quantities of drugs to fight neglected tropical diseases.

But sometimes impecuniousness has its advantages. Or at least so suggests William H. Foege in his new book, “House on Fire: The Fight to Eradicate Smallpox”.

Foege (pronounced Faygee) was a medical missionary and epidemiologist working in Nigeria in 1966 when he was asked to assist in the World Health Organization effort to stamp out smallpox, which was launched earlier that year. Although there was no treatment for the disease, there was a vaccine in use for150 years that could prevent scarring, blinding, and an often fatal infection. The strategy was to vaccinate everyone then go after outbreaks with targeted immunization campaigns.

The trouble was that when word arrived in December 1966 about a smallpox outbreak in Ogoja province, Foege and colleagues, working for what’s now known as the Centers for Disease Control and Prevention, didn’t have enough vaccine for a province-wide campaign. So they vaccinated only the infected villages and three others within a 15-mile radius. Within weeks, the outbreak extinguished itself like a fire without fuel.

As a result of that experience, surveillance-and-containment (better known as “ring vaccination”) became the primary tool of the smallpox campaign. It saved money, manpower and vaccine. It probably made eradication possible. The last wild case occurred in Merca, Somalia in October 1977.

Smallpox is the only human disease to be eradicated. The director of the global campaign, D.A. Henderson, published his own memoir of the effort, “Smallpox: The Death of a Disease,” in 2009. Rinderpest, a devastating measles-like infection of cattle, recently became the first eradicated animal disease.

Foege, 75, went on to an illustrious career as director of CDC, director of the Carter Center, and now senior fellow at the Bill and Melinda Gates Foundation.

Ring vaccination doesn’t work as well against polio, a disease in which most cases are invisible. With a less effective vaccine and the need for frequent vaccination of all children in places where that virus still circulates, the polio eradication campaign is now more than a decade past its targeted deadline. But Foege is confident.

“Polio will disappear. There’s no question in my mind,” he said during a recent visit to The Post.

He added that “no field in medicine has changed as much in 10 years as global health.”

It’s not just the Gates Foundation, the President’s Emergency Plan for AIDS Relief (PEPFAR), and the Global Alliance for Vaccines and Immunization (GAVI) that have changed the landscape. There’s also the emerging “public-private partnerships” such as Merck’s multi-decade investment in the elimination of onchocerciasis (river blindness); GlaxoSmithKline’s in the fight against lymphatic filariasis (elephantiasis); and Pfizer’s in the campaign against trachoma, another blinding infection.

“In global health you used to think like a poor person — how to use the small resources you had and be grateful,” said Foege, who is six-feet, seven-inches tall but has the self-effacing manner of a man who perhaps thinks he takes up too much room. “People going into [global health] today can think big.”