Viruses and the Virome

December 2021 3:41 min

WHAT IS A VIRUS? - Visual Description Transcript

[HARPSICHORD MUSIC]

[In an animated scene, a group of people in 17^th century Dutch clothes stand near a canal in old Amsterdam. In the background, a swirling, blinking line slithers through the city’s buildings.]

NARRATOR: In the 17th century, a sickness was sweeping through Amsterdam.

[The swirling line coils into a spinning spiral which grows to take up the hole frame, and then shrinks down to reveal an Old Master painting of Dutch men with animated, loopy spirals over their eyes.]

NARRATOR: People were driven to madness by... tulips.

[An animated tulip pushes the frame of the old men off screen and flourishes its petals. The tulip pulls up a 17^th century Dutch still life of a vase of beautiful flowers.]

NARRATOR: 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.

[The camera tracks down past the painting to reveal the animated tulip’s bulb. Many gold coins appear around it.]

NARRATOR: One 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!

[A drawing of tulips with striped petals dissolves into an archival illustration of broken tulips—their petals streaked with alternating bands of white and color. This illustration then dissolves into a microscopic image of potyvirus—a virus related to that which causes the tulip-breaking disease.]

NARRATOR: Two hundred years later another sickness swept through the Netherlands.

[A cartoon windmill overlooks a field of animated plants.]

NARRATOR: This time, though, it didn’t result in pretty flowers, but in dying tobacco plants.

[The tobacco plants’ leaves wither and shrivel.]

NARRATOR: 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.’

[Small, blurry shapes are shown in a view through a microscope. The microscope lenses increase magnification, but the objects remain blurry. Finally, they resolve into the word “virus.”]

NARRATOR: Today, we’re able to see viruses using electron microscopes, and we’re learning more about how they operate.

[A scientist sits at her electron microscope. Cartoon images of a virus move around on her screen. We zoom in to get a closer look.]

NARRATOR: We know that viruses are basically just instructions for making more viruses—pieces of genetic material wrapped inside shells and looking to reproduce.

[A cartoon virus spits out several copies of itself.]

NARRATOR: But they don’t crawl or swim or replicate at all on their own.

[SNEEZE]

[The scientist at her microscope looks at the cartoon viruses. She sneezes and the slithering line representing the path of transmission snakes out.]

NARRATOR: They need to be spread to a host. Bacteria, tulips, turkeys, and humans—we’ve all got them. Viruses infect every living thing and may be as old as life itself. The vast majority aren’t harmful to humans at all.

[The camera tracks the path of the sneeze, passing a cartoon bacterium, tulip, turkey, and human. The scene wipes to an animated Earth rotating in space. Dozens of animated viruses, in various forms and colors spread out from the globe.]

NARRATOR: 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.

[A large animated herpes virion floats through a landscape of people walking.]

NARRATOR: Other kinds of viruses showed up as people started domesticating animals and living together in large groups—things like measles and smallpox.

[The camera continues to move across the landscape. A barn and cows appear in the foreground, and animated smallpox virions rise up behind them.]

[COW MOOS]

NARRATOR: Lately, new kinds of viruses are appearing. These ‘emerging’ viruses often pop up when humans or farm animals come in contact with wildlife. They’re not so much new as new to us.

[As we move past the landscape, a cityscape towers above and there are many more silhouettes of people walking. The buildings encroach on a forest and a cartoon bat flies out.]

NARRATOR: A virus that originally evolved to infect bats might mutate and jump to a camel.

[A rotating diagram appears—the circular outline of a virus contains “windows” that reveal a bat and the word “BAT.” The animal and the word rotate, revealing a camel and the word “CAMEL,” in the same windows.]

NARRATOR: As the virus reproduces inside the camel’s cells, maybe this time it mutates into a form that can infect humans.

[The diagram rotates again, and the camel gives way to a human and the word “HUMAN.”]

NARRATOR: That’s exactly what researchers think happened with a coronavirus named MERS.

[The word “MERS” appears in the center of the diagram and the images rotate again to reveal a bat.]

NARRATOR: MERS and infections like it are called zoonotic diseases—they arise when viruses hitch a ride from animals to humans.

[The word “ZOONOTIC” appears. Behind it the silhouettes of a human and a pig appear.]

NARRATOR: Some 60 percent of all human infectious diseases hop from or between other species before moving into us.

[A pie chart appears in the shape of a circular virus. Approximately 60 percent is colored in and labeled “Zoonotic”. Names of zoonotic diseases appear around the edges of the chart: LYME DISEASE, BIRD FLU, SLEEPING SICKNESS, MALARIA, RABIES, YELLOW FEVER.]

NARRATOR: 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.

[A simple representation of the SARS CoV-2 virus gives way to a similarly shaped representation of a bat virus, labeled RaTG13. Animated bats fly in the background.]

NARRATOR: When we clear forests, build massive industrial farms, and fuel climate change, we create new pathways for viruses to reach us and beyond.

[A conveyor belt carries forests, farm buildings, and factories. As they fall off the edge, virus forms and human silhouettes appear.]

NARRATOR: 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.

[Humans and viruses are followed by trees and a bat, representing naturally-evolved ecosystems. Those, in turn, give way to domesticated animals and other virus forms.]

NARRATOR: Viruses, 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.

[An illustrated group of people stand in front of a field of tulips. Virus forms float behind them.]

NARRATOR: 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.

[Viruses, tulips, and a variety of animals (including a human) surround an animated Earth, spinning in space.]

[Credits roll.]

Our Balancing Act with Viruses

From the depths of the ocean to the tops of mountains, everywhere there’s life on Earth, there are viruses—including within our own bodies.

You may have heard of the human microbiome, the communities of bacteria and other microbes that live on us and inside us. “Scientists estimate that we have roughly as many bacterial cells hanging out in or on each of us as we have human cells,” says Rob DeSalle, curator in the Museum's Division of Invertebrate Zoology.

And just as we have a microbiome, we also have a virome. Tens of trillions of amazingly diverse viruses call us home.

Most of the viruses inside our bodies are bacteriophages that attack bacteria rather than human cells. Bacteriophages, like the one shown here in red, are the most abundant biological entities on the planet.
Courtesy of M. Dürrenberger, Biozentrum, University of Basel

Bacteriophage T4 has a spider-like appearance.

Electron micrograph of a human herpesvirus-6 virus shows 5 circular "eyes" on its surface.

The circular “owl’s eyes” in this image are HHV-6, or the human herpesvirus-6. HHV-6 infects nearly every human, usually before we reach the age of three, and can remain dormant, but present, for the rest of our lives.

Microscopic image of a single SARS-CoV-2 virus.

SARS-CoV-2 virus, as imaged by a transmission electron microscope. The virus’ surface projections form the crown for which coronaviruses are named. The Latin word corona means “wreath” or “crown.”

The ones that spring to mind first, of course, are those that cause disease. But disease is only a small part of the story. Wherever scientists look in or on our bodies, they find communities of viruses: in our blood and our guts, on our skin, in our mouths and our lungs, in our nervous and reproductive systems. These viruses vary enormously from person to person. Many are benign or helpful. Some are not even there to infect our own cells.

Viruses helped shape our evolution and make us who we are.

Given the abundance of bacteria in the human microbiome, most of our viral colonizers are probably phages: viruses that depend on bacterial hosts, infecting them and replicating within them. Sometimes phages kill their host bacteria, sometimes they add their DNA to that of the host, and sometimes they just hang out and wait for the right conditions to act. As part of a complex microbial ecosystem within us, the phages in our virome can affect the balance of bacteria in our microbiome—which in turn affects our health.

Other important members of our virome can affect us more directly, by infecting human cells. We know a lot about some of these, particularly the ones that cause disease. Some of them can make us acutely sick, while others may infect our cells without causing illness for long periods of time, or perhaps ever.

But many of the viruses that infect human cells appear to be benign passengers. Some have been with us for thousands or even millions of years. Their ancestors infected our ancestors. They evolved with us as we evolved. And because many viruses can insert their own genetic material into their hosts’ DNA, viruses are an intimate and consequential part of our history.

For example, mammals need a protein called syncytin to build a properly functioning placenta, which nourishes and protects growing embryos. The gene for syncytin comes from a virus that infected an ancestral mammal more than 100 million years ago. If it weren’t for that virus, we might never have been born.

Illustration of an opposum-like mammal about to eat an insect off a leaf.

An artist’s rendering of the hypothetical ancestor of all placental mammals. A virus carrying the syncytin gene may have been crucial for development of the placenta.
© C. Buell

Whenever we encounter a new dangerous virus, our immune system springs into action to recognize it and defend us, using tools our ancestors developed over the course of millions of years from their encounters with previous pathogens, including viruses. Vaccines work by alerting the immune system to be on the lookout for a particular virus or other pathogen; advance warning can make all the difference.

For good and ill, viruses helped shape our evolution and make us who we are.

Viruses and the Virome

Our Balancing Act with Viruses

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