Almost 100 years ago, an outbreak of the flu swept across the world, killing an estimated 20 million to 50 million people and affecting hundreds of millions more.

In the century since, we've made impressive leaps in our ability to study pathogens and track their movement between animals and people, and from one country to the next. But scientists and public health officials say we are at greater risk today for a pandemic due to our growing population, our global nature, and rising temperatures that allow insects carrying viruses like Zika to spread to more of the planet. Echoing these concerns, Time magazine recently declared we aren't ready for the next pandemic.

As Ebola breaks out again in Africa and officials warn about the risk of Zika in the U.S. this summer, we asked four researchers what our top priority should be if we want to survive the next pandemic.

• Anne Rimoin, epidemiologist, UCLA: We need to study outbreaks in real-time.
• Jason Cone, USA executive director, Doctors Without Borders/Médecins Sans Frontières': Governments play the greatest role in protecting people.
• Peter Hotez, pediatrician and dean, National School of Tropical Medicine, Baylor College of Medicine: Protect the "soft underbelly" of the U.S.
• Ali Khan, public health expert and dean, College of Public Health, University of Nebraska Medical Center: Pandemics are as dangerous as war.

Until recently, physicist Brian Greene says he never made a comment on anything that didn't have to do with relativity or quantum physics. Now, he's stepping out, like some other scientists who marched on Washington in April or are considering running for public office, because he feels science is under siege.

I spoke with Greene, who with his wife co-founded the World Science Festival, an annual event that takes place next week in New York, about his hopes to shift people's perspective on science and build confidence in it.

The takeaways:

• Science is more fluid than "it's right or it's wrong."
• Arguments over the early universe shouldn't discredit what cosmology has done so far.
• The most exciting thing the Large Hadron Collider could do is find something totally unexpected and send us all back to the drawing board.

Read more of the interview here.

1. Zika's path: Sequences of the virus reveal how it spread through the Americas and went undetected for months in many places.
2. Postcard from Jupiter: NASA's Juno probe finds chaos on the planet.
3. Fine-tuning the tomato: Manipulating a genetic sweet spot to get more tomatoes from a plant.
4. Origins: A team suggests humans originated in Europe not Africa, but their case isn't convincing many.

1. How diseases get names: "The Spanish flu stands as a monument to the ugly history of disease naming," Laura Spinney writes in Aeon.
2. The tale of the 3D printed mouse penis: Ed Yong's humorous piece about what scientists carry in their suitcases through airport security. (Reminds me of the time my dad was stopped in Denver with a tube of DNA dye I gave him from my lab).
3. Body sense: New research on how we perceive and control our bodies is informing therapies for people who've lost their sense of self.

It was a controversial move, but in 2005 scientists recreated the 1918 flu virus and looked at its effects on mice. Those in favor had argued that resurrecting the virus and studying it with modern molecular biology techniques could help fight future flu pandemics. Those against it thought it was too risky — terrorists could use the published sequence to make their own viral arsenal, they argued.

How they did it: A team of researchers extracted fragments of the virus from hospital samples and a flu victim who had been frozen in the Alaska permafrost since 1918. The RNA was changed into DNA, sequenced, and those sequences were fit together to get the full genome of the virus. Next they synthesized the virus DNA from the sequence, and injected it in human kidney cells to manufacture lots of the virus. When it was injected into mice, the virus was unexpectedly lethal — all died within six days.

What they learned: They then replaced some genes in the 1918 virus with others from modern, less deadly strains and identified the genes that gave the 1918 flu its virulent power and the ability to be passed between people.

The legacy: It wasn't the first virus recreated, but the research on the 1918 flu paved the way — philosophically as much as scientifically — for others to resurrect ancient viruses in the name of public health and medicine. And, a larger debate still continues about whether we should revive extinct species.

This high-resolution image shows the 300-meter-wide plough mark of a flat-bottomed iceberg that was dragged across the floor of the central Barents Sea (north of Norway) by currents and tides. When the ice sheets there started to melt, probably 12,000 -15,000 years ago, the sea level was about 80 meters lower than today and the masses of ice left their mark, says marine geophysicist Kelly Hogan from the British Antarctic Survey. She's an editor of the Atlas of Submarine Glacial Landforms.