What is a virus?

0:01>>NARRATOR: In the 17th century, a sickness was sweeping through Amsterdam. People were driven to madness by... tulips. At one point of this tulip mania, it cost less for a famous painter to paint you a still life of tulips than it did to buy a single rare bulb.

0:20One of the most desirable of all was the ‘broken tulip.’ Scientists later learned its special look was caused by a virus, but no one knew that at the time. We didn’t even know that viruses existed! 200 years later another sickness swept through the Netherlands.

0:38This time, though, it didn’t result in pretty flowers, but in dying tobacco plants. Researchers discovered that this disease was caused by something so small it couldn’t even be seen under a microscope. One researcher dubbed it a ‘virus.’ Today, we’re able to see viruses using electron microscopes, and we’re learning more about how they operate.

1:02We know that viruses are basically just instructions for making more viruses—pieces of genetic material wrapped inside shells and looking to reproduce. But they don’t crawl or swim or replicate at all on their own. [SNEEZE] They need to be spread to a host. Bacteria, tulips, turkeys, and humans—we’ve all got them.

1:25Viruses infect every living thing and may be as old as life itself. The vast majority aren’t harmful to humans at all. Of the viruses that infect humans, some, like herpes viruses, evolved along with us. Almost every human on the planet has them and generally, they’re not deadly.

1:47Other kinds of viruses showed up as people started domesticating animals and living together in large groups—things like measles and smallpox. Lately, new kinds of viruses are appearing. These ‘emerging’ viruses often pop up when humans or farm animals come in contact with wildlife.

2:06They’re not so much new as new to us. A virus that originally evolved to infect bats might mutate and jump to a camel. As the virus reproduces inside the camel’s cells, maybe this time it mutates into a form that can infect humans. That’s exactly what researchers think happened with a coronavirus named MERS.

2:28MERS and infections like it are called zoonotic diseases—they arise when viruses hitch a ride from animals to humans. Some 60 percent of all human infectious diseases hop from or between other species before moving into us. SARS-CoV-2—the virus behind COVID-19 that sparked a pandemic and global economic crisis—was first identified in 2019 and quickly recognized as closely related to a virus found in horseshoe bats.

3:00When we clear forests, build massive industrial farms, and fuel climate change, we create new pathways for viruses to reach us and beyond. By destroying natural environments, we disrupt protections that evolved over millions of years, putting both the species that live there and the species causing the destruction—us—at greater risk.

3:24Viruses, tulips, and humans are all interconnected and to see us only as separate or opposing forces is to miss an opportunity for scientific understanding and saving lives. Part of fighting disease in the future will be protecting our planet’s ecosystems and studying both viruses and the incredibly diverse organisms that host them.