Today, Bill and Melinda Gates released their Annual Letter. This year the letter is addressed to Warren Buffett, who donated the bulk of his fortune to the Bill & Melinda Gates Foundation 10 years ago, and focuses on the gains that have been made since then to improve health of children around the world.

Bill and Melinda use the letter to highlight numbers that tell a story of how the world is doing in several different areas – 48 million children saved since 2000, 300 million women in the developing world who use contraceptives. But they say there is one number they work toward every day: zero.

As Bill and Melinda explain in their letter, the “magic number is zero” when thinking about many of the health challenges we face today – ending malaria, TB, HIV – and polio is the closest to reaching this goal. Bill and Melinda discuss the persistence and dedication of health workers around the world and Rotary International in achieving this magic number.

It is in part because of the contributions from Warren and other generous donors that the world has made this incredible progress – and now zero is in sight.

Read the full letter here: gatesletter.com

Hear from Ann Lee Hussey, a polio survivor and volunteer for Rotary International, as she shares her story of living with polio. Her experiences drive her commitment to reach zero and end the disease once and for all.