Bill Gates speaks on stage at the 2015 Clinton Global Initiative's Annual Meeting on September 27, 2015 in New York City. JP Yim/Getty Images Polio has been disappearing worldwide for the last 40 years — only 37 people are said to suffer from the disease today.

But the Bill and Melinda Gates Foundation still has concerns about the disease making a comeback, particularly if the Trump administration's budget cuts to foreign aid limit how much philanthropic bodies can work with the US on public health projects in at-risk countries.

Rob Nabors, director of US policy, advocacy, and communications at the Gates Foundation, says the organization's main role is offering data and best practices to countries so they can make smart health investments themselves.

Budget cuts could mean less interaction between the Gates Foundation and the US government, including its work with the Global Polio Eradication Initiative and a number of other federal programs. At-risk countries wouldn't receive as much help in those cases.

The proposed cuts are significant — the biggest since the 1970s. If approved, Trump's budget would shrink the foreign-aid budget by 31%, from $30 billion in 2017 to $20.7 billion in 2018. The current budget makes up less than 1% of the $3.8-trillion federal budget.

Local health workers carry vaccination kits at a distribution center ahead of the start of a nationwide polio immunization campaign on Wednesday, in Lagos Thomson Reuters

For polio, a disease on the brink of extinction, that kind of cut could be troubling. Since 1987, polio cases have dwindled dramatically. By 1994, all of North and South America and China had eradicated the disease. Europe was polio-free several years later, and India's last case came about 15 years after that.

Much of that progress has come from significant investments in education and vaccination, Nabor says. And it's come over a period of decades as organizations like the Gates Foundation have built trust in local communities. Citizens have come to understand what vaccines do, and leaders have come to see the economic benefits they offer over the long haul.

If eliminated, polio would be just the second disease after smallpox to see full eradication. But less federal funding for those types of programs could lead to a scenario in which polio cases start to rise in African and Middle Eastern countries, Nabors tells Business Insider.

"Absent those types of investments, it's not as if we'll just be frozen at those single-digit cases," he says. That could then force governments to spend more of their base funding on polio instead of other areas where they've also begun to make progress.

File photo of a girl receiving polio vaccine drops at a government dispensary in a Karachi slum Thomson Reuters

To avoid a backward slide in global health, Nabors points to a few safeguards that organizations can put in place.

The first is educating new leaders on the role that global-health investments around the world play in fostering international stability and economic growth. Bill Gates, for example, recently met with President Trump to discuss the importance of vaccines and global safety, a discussion that Gates later said seemed to stick with the president.

Bill Gates visits Trump Tower in New York City. Andrew Kelly/Reuters The second is specific to Bill and Melinda Gates, who have become savvy businesspeople that can sell large-scale investments to political leaders. Nabors mentions the returns on investment the Gateses have relayed to leaders when it comes to immunizing their citizens: Healthier children grow up to become more productive members of society. In Asia, for example, 30-50% of the economic growth between 1965 and 1990 has been chalked up to reductions in infant and child mortality.

Finally, Nabors says organizations need to make at-risk communities seen and heard. They need to be present in leaders' minds, particularly so that governments see how close the world is to never having to deal with polio again.

"I don't think people realize that in 2017 and 2018, we could be in a place where we've eradicated polio," Nabors says. "That's a big deal. And it's up to us to explain to audiences in the developed world what that means and how important the leadership of these countries actually is."