Billionaire philanthropist Bill Gates has spent the past couple decades warning the general public about ominous issues, from upcoming "climate disasters" to devastating cyberattacks.

Two potential catastrophes evoke the most concern from Gates. "A lot of unrest" in today's world could spark "a major war," he tells CNBC Make It. And even "if we avoid a big war ... then, yes, there will be another pandemic, most likely in the next 25 years."

Scientists typically view pandemics as likely, even inevitable, occurrences over time. They are indeed becoming more common, due to factors like climate change and population growth, research shows.

For Gates and other global health advocates, the question isn't whether another pandemic will occur soon — it's whether nations will be more prepared than they were for the outbreak of Covid-19. "The country that the world expected to lead and be the model fell short of those expectations," Gates says, referring to the United States.

Gates wrote a book called "How to Prevent the Next Pandemic" in 2022, in which he called out various governments, including the U.S., for not being adequately prepared in 2020. In the book, he laid out several recommendations for countries worldwide, including stronger quarantining policies, investing in disease monitoring and boosting vaccine research and development.

While some progress has been made, with increased spending on pandemic preparedness in the U.S. and elsewhere, Gates says the global response hasn't yet been enough. "Although some of the lessons from [the coronavirus] pandemic have been learned, [it's been] way less than I would expect, sadly," he says.

The political divisions many believe hampered the world's response to Covid-19 are still standing in the way of preparing appropriately for the next outbreak, Gates adds: "Getting our thoughts together about what [we did] well, what we didn't do well, is still not happening .... Perhaps, in the next five years, that'll get better. But, so far, it's quite surprising."

Preventing widespread disease is the focus of an episode in the upcoming Netflix docuseries "What's Next? The Future with Bill Gates," set to premiere September 18.

In an advance screening of the Netflix series provided to Make It, Gates sits down with Dr. Anthony Fauci, the former director of the National Institute of Allergy and Infectious Diseases. In that conversation, Fauci is adamant that the wealthiest nations, like the U.S., have a "moral responsibility" to share their abundant resources to lead the way on preventing the spread of disease around the world.

Fauci published a memoir this summer called "On Call," in which he expressed his concerns over how the world is facing a "crisis of truth" over rampant misinformation, such as the kind that shook the public's faith in public health initiatives.

The scientist struck a more optimistic tone in a July interview with People, in which he said he believes that public trust of scientific facts will eventually be restored.

"I still feel as somewhat of a cautious optimist that there are the better angels in everybody that will come out," Fauci said.

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