Good morning, Hank. It's Tuesday.

I need a bit of encouragement at the moment, so let me tell you the most encouraging fact I know.

So I graduated from high school in 1995, before most of our viewers were born. That is not the encouraging fact, that's actually quite distressing. But anyway, in 1995, over 11 million children died before the age of five. Last year, fewer than five million children died before the age of five.

Since I graduated from high school, overall global child mortality has fallen by well over 50%. Now, it's still far too high—we could reduce it by another 50% with existing technology if we really wanted to. That’s actually one of the most discouraging facts I know is that we could choose to live in a much better world than we're currently choosing. But this is not about being discouraged.

Anyway, this progress, which I will argue was not natural, or normal, or inevitable, represents, I think, the greatest success in human history.

We can also understand this as the likelihood of a child dying. In 1800 in the United States, about 46% of all people born died before the age of five. That’s similar to what the rate had been 500 or 5,000  or 50,000 years earlier. Forty years later, by 1840, it had only gone down to 43%—extremely slow progress.

Progress continued throughout the 19th century, albeit slowly, thanks to better sanitation, emerging understanding of the germ theory of disease, and so on. But then, in the 20th century, things changed dramatically. In the 40 years between 1920 and 1960, your chances of dying under the age of five went from 18% to 3%.

And a lot of things had to go right for that to happen: better pharmaceutical interventions like insulin and antibiotics, safer surgery, lower rates of absolute poverty and malnutrition, lower rates of tuberculosis, and so on. But whether we're talking about the U.S. or globally, none of this happened naturally. It is not natural for the world population to become less hungry or less sick.

Our species is around 300,000 years old, and for way over 99% of that time, no meaningful progress was made when it comes to child mortality. None. About 120 billion modern humans have ever lived, and most never saw the age of 20. If you are born in the United States now, you have a 99.1% chance of living to the age of 20. After 300,000 years of not being able to get half of people to adulthood, we now know how to get 99% of people there.

Now, there’s nothing simple about how we reduced child mortality by more than half since I graduated from high school. Some of it is because absolute poverty declined dramatically. In 1995, about 36% of people lived in absolute poverty; today, about 10% do. And that means people overall are less hungry, which decreases direct deaths from malnutrition but also decreases the deaths that come from the weakened immune system that accompanies malnutrition.

Also, safer circumstances in which to give birth have decreased both maternal and infant mortality. Some small part of the story can be attributed to nonprofit organizations that fund stronger healthcare systems. But one of the central reasons we've seen child mortality go down so much since 1995 is government-funded interventions, including those funded by the U.S. government, like PEPFAR and the Global Fund.

PEPFAR, a program aimed at fighting HIV/AIDS in impoverished communities, has been hugely successful, saving over 25 million lives and preventing millions of children from being born HIV-positive. And the Global Fund to fight malaria, AIDS, and tuberculosis has also saved literally millions of lives.

From an alleviation-of-suffering perspective, these are some of the best things we have ever done together as a species. Which is why I am so heartbroken that PEPFAR, and funding for the Global Fund, and almost all other foreign aid has been completely frozen by the new administration in the United States.

I talk a lot about how many people still die of tuberculosis, which kills over 1.25 million people each year even though it's curable and preventable, which is just absolutely unconscionable. But perhaps I don't talk enough about how many people used to die of tuberculosis. In 2000, the year I graduated from college, 2.6 million people died of TB. This means we've reduced TB deaths by over 50% just in the last 25 years. Now, this progress has been far too slow, but it is progress. More affordable tests and treatments can accelerate that progress, as we've started to see in the last couple years. But I want to be clear: that progress is not guaranteed. It is not natural.

We know it's not guaranteed because, in rich countries, tuberculosis is actually on the rise. This year, the U.S. will see around 10,000 cases of active tuberculosis. Which is a reminder that this is an airborne disease. TB anywhere is a threat to humans everywhere.

And we know that if this so-called "pause" on aid is not amended to exclude diagnostics and medication, many, many people will die. Interrupting the flow of HIV medication can be life-threatening, as can stockouts of TB drugs. Even a couple of weeks without TB treatment gives the bacteria a chance to evolve resistance, which makes the infection much more likely to be fatal, but also means there’s more drug-resistant tuberculosis circulating. That's a threat to everyone. Because again, this progress we've had is not inevitable. It is the result of sustained, ongoing, open-ended funding and collaboration.

I really hope that in 30 years, I’m able to say that the most encouraging fact I know is that we continued to reduce child mortality throughout my entire lifetime.

Continued progress for human health is not natural. It will result, or fail to result, from human choices.

Hank, I'll see you on Friday.