To help you understand what a virus is, we present you with some surprising figures and information about their coexistence with humans.
They’re as old as life itself but scientists can’t say for sure if they’re alive. Viruses are written into our DNA, shaping the human saga through mutation and resilience.
They’re even in our blood. People touch hundreds of millions of them every day. As the Covid-19 outbreak disrupts global markets and prompts unprecedented containment measures, it is worth asking a very basic question: what, precisely, is a virus? What are they made of? Where did they come from?
While their beginnings are uncertain, viruses have left their imprint on nearly all life on Earth, including humans.
Around 8% of the human genome is of viral origin – that is, the remnants of ancient viruses that have infected us, developing species-wide tolerance.
But their story begins aeons before humans. “We think that viruses were there at the very
beginning (of life on Earth),” says Curtis Suttle, a virologist from the University of British
The story of viruses is perhaps best told through mind-bending figures. According to Suttle, the physical properties of viruses make them hard for humans to comprehend.
Their tiny size, for starters. If each virus in a human body grew to the size of a pinhead, the average adult would become 150 kilometers tall. In a 2018 study, Suttle found more than 800 million viruses settle on each square meter of Earth every single day.
A 2011 paper published in Nature Microbiology estimated that there are more than one quintillion (1 followed by 31 zeros) viruses on Earth.
Lay them all end to end, and they’d stretch 100 million light years, or 1,000 times the breadth of the Milky Way.
The virus as concept
Viruses are best thought of as “molecular packages”, according to Teri Shors, professor of biology at the University of Wisconsin Oshkosh and author of several books on the subject.
Essentially strings of genetic material contained by a few protein molecules, viruses occupy a strange middle ground between the living and the inert. “These packages have to be small enough to fit inside of a cell to cause infection,” explains Shors.
As soon as they enter their host, viruses hack cells with new genetic instructions to replicate at dizzying speed.
Are all viruses bad?
Most viruses come to our attention because they make us sick. Recent years have seen widespread outbreaks of viral infectious diseases, from the coronavirus epidemic today to SARS in the early 2000s and Ebola in western and central Africa.
But there are virtuous viruses too. “Nearly all viruses are in fact harmless to humans,” says Ed Rybicki, a virologist at the University of Cape Town. Indeed, many viruses benefit human health, infecting other organisms that would otherwise do us harm.
Another benefit: the carbon uptake of ocean algae, which helps purify the air we breathe, is greatly accelerated by viruses.
And they have widespread healthcare applications. Besides vaccines derived from weakened viruses, an emerging area of treatment known as virology is developing new ways to treat chronic diseases such as cancer.
For Rybicki, who has spent most of his professional life trying to unlock their secrets, the most remarkable thing about viruses is how many more mysteries they still hold. “They are the most diverse organisms on our planet (…) and we still know hardly anything about them.”
The recent finding of giant viruses shows that they’re still capable of surprising us.
With information from AFP.