Nothing demonstrates human interconnectedness like the spread of infectious disease.

Polio is now endemic to just three countries: Afghanistan, Nigeria and Pakistan. In recent years, visitors have carried it back to 39 previously polio-free states.

Thus people everywhere have a stake in eradicating polio, as we have stamped out smallpox. Immunizing the last unvaccinated children on the planet is an expensive and complex undertaking, and worth it in the long run.

The world not only would be forever spared an incurable, crippling and often fatal disease, it also would save money. If polio transmission could be stopped by 2015, the net benefit from reduced treatment costs and productivity gains through 2035 would be $40 billion to $50 billion, according to a 2010 study.

Thanks to the efforts of the Global Polio Eradication Initiative — which links national governments to the World Health Organization, the U.S. Centers for Disease Control and Prevention, UNICEF, Rotary International and the Bill & Melinda Gates Foundation — progress has been tremendous.

Polio cases dropped from 350,000 in 1988 to 60 so far this year. In the same period, endemic countries fell from 125 to three. Remarkably, India, which because of population density and poor sanitation was considered the greatest challenge, had zero polio cases last year.

Just as the eradicators were closing in, the job’s completion has been threatened by a $1 billion funding gap in the global initiative’s $2.19 billion budget. The shortfall was caused by reduced government donations in an economic slowdown and the unexpectedly high costs of eliminating the last pockets of polio transmission.

To cope, the coalition has adopted an emergency plan that prioritizes efforts in the three endemic countries while reducing vaccinations in 24 high-risk countries. The idea is to stop the virus at the source and hope it doesn’t spread to places where vigilance has been eased.

The risk is that without sufficient resources, the whole effort will break down. Controlling polio has taken an orchestrated, $9 billion global effort, sustained by the goal of exterminating the disease. If polio spreads again, the campaign may lose its ability to raise significant funds.

Worse, if the eradicators lose their tight grip on the disease, polio experts estimate there could be 200,000 new cases of the disease a year.

The United States has done its share to support the effort, its government and charities having provided a quarter of the GPEI’s funds. China, which has experienced outbreaks of polio imported from Pakistan, can afford to start contributing. The oil-rich Gulf states could be more generous. Pakistan could pick up a greater share of its costs, as Nigeria and India have.

The world has come too close and the stakes are too high for polio eradication to fail.

Editorial by Bloomberg View