The Hidden World of Viruses Inside Us
The Unseen World of Viruses
The viruses we know best are the ones that make us sick — the influenza viruses that send us to bed and the smallpox viruses that may send us to the grave. But healthy people are rife with viruses that don’t make us ill. Scientists estimate that tens of trillions of viruses live inside of us, though they’ve identified just a fraction of them. A vast majority are benign, and some may even be beneficial. We don’t know for sure, because most of the so-called human virome remains a mystery.
The Human Virome Program
This year, five universities are teaming up for an unprecedented hunt to identify these viruses. They will gather saliva, stool, blood, milk, and other samples from thousands of volunteers. The five-year effort, called the Human Virome Program and supported by $171 million in federal funding, will inspect the samples with artificial intelligence systems, hoping to learn about how the human virome influences our health.
The Early Discovery of Phages
The first hints of the human virome emerged over a century ago. Analyzing stool samples, scientists discovered viruses known as phages that could infect bacteria inside the gut. Phages also turned up in the mouth, lungs, and skin.
A Vast and Diverse World
Scientists later found viruses that infected our own cells without causing any major symptoms. A vast majority of the world’s population gets infected with cytomegaloviruses, for example, which can colonize just about every organ. In the early 2000s, new genetic sequencing methods led scientists to find yet more viruses in saliva, blood, and stool. The technology also allowed them to estimate the number of viruses in our bodies by counting copies of viral genes. Each gram of stool, it turned out, contains billions of phages.
How Many Species of Phages?
Each person’s gut may harbor hundreds or even a thousand species of phages. But when biologists go from person to person, they will find many viral species in one that are missing from another — even when those people are married. The more people scientists study, the more species of phages they discover. "I’m expecting tens of millions of species," said Evelien Adriaenssens, a phage biologist at the Quadram Institute in Norwich, England.
The Complexity of the Human Virome
The viruses that infect human cells have turned out to be unexpectedly diverse. In 1997, researchers in Japan inspecting the blood of a patient discovered an entirely new virus family that came to be known as anelloviruses. Last month, a study revealed over 800 new species of anelloviruses, bringing the total number of known species to more than 6,800.
New Tools for Discovery
Some recent studies about the human virome raise questions about the very definition of a virus. A standard virus consists of a protein shell holding genes that are encoded either in double-stranded DNA or single-stranded RNA. But scientists are finding that our bodies are also home to exquisitely tiny rings of free-floating RNA. "Totally new tools are going to have to come in," said Dr. Pardis Sabeti, a computational biologist at the Harvard T.H. Chan School of Public Health.
Conclusion
The human virome is a vast and complex world, full of mysteries waiting to be uncovered. As scientists embark on this unprecedented journey, they will uncover new species of phages, viruses, and other microorganisms that live inside of us. But they will also discover how these microorganisms interact with our bodies and impact our health. The findings will challenge our understanding of viruses and open up new avenues for research and treatment.
FAQs
Q: What is the human virome?
A: The human virome refers to the collection of viruses that live inside the human body.
Q: How many viruses live inside the human body?
A: Scientists estimate that tens of trillions of viruses live inside the human body, though they’ve identified just a fraction of them.
Q: What is the purpose of the Human Virome Program?
A: The Human Virome Program is a five-year effort to identify and study the viruses that live inside the human body and how they impact our health.
Q: What is the scope of the Human Virome Program?
A: The program will gather saliva, stool, blood, milk, and other samples from thousands of volunteers and use artificial intelligence systems to inspect the samples and learn about how the human virome influences our health.
