The world’s progress in fighting polio might be one of the best-kept secrets in global health.

Since 1988, the number of annual cases has dropped more than 99.9 percent. There used to be an estimated 350,000 children paralyzed by polio every year; so far this year, there have been just 48 cases. Only two countries, Pakistan and Afghanistan, have never been free of the disease. And yet I’m often surprised to hear how many people don’t know about this mind-blowing progress.

The credit goes to an international coalition of people fighting the disease: the volunteers and front-line health workers who go out and deliver vaccines, the leaders who make it a priority, the funders who underwrite the work. (For example, support from the United Arab Emirates has been key to vaccinating children in Pakistan.) Thanks to all these efforts, we are achingly close to eradicating polio. Now we need to finish the job.

October 24 is World Polio Day, and I wanted to mark the occasion by writing a thank-you letter to everyone involved.

To everyone involved in the fight against polio,

Ten million children are alive and walking today because of your efforts to eradicate polio.

They will never know your names or what you have done for them. But if they did know, I believe they would want to say: Thank you.

Thank you for everything you are doing to wipe out this crippling disease.

Thank you for blanketing the world’s largest cities and its smallest villages—sometimes even risking your own lives—to make sure every child is protected from polio.

We have come so far—more than 99 percent of the way—and eradicating this disease is within our reach, as long as we keep up the effort.

For me personally, it is an honor to support your amazing work. One day we will come together to celebrate the end of polio, and the world will know that it was only possible because of what you are doing.

You have my admiration and my gratitude.

Sincerely,

Bill Gates