Bacteria have a better popular reputation than viruses these days. It’s not science, but it is culture.
You can see it in all the feel-good marketing for gut bacteria and yogurt as medicine for the human microbiome, and in lifestyle stories about better living through kimchi and fermented pickles. Even at the extreme of fecal transplants, people will take their bacteria any way they can get them.
Viruses have no such sheen of benevolence. Usually they are ignored, or seem to be other people’s problems, or are the better of two possibilities when a bad cough comes on. “Just a virus,” they say, no need for antibiotics. But after a week that saw a scary new disease grow from yet another worrying news story into a generational terror, the pathogen having its big moment in the glare of popular attention these days is the virus.
This germ favouritism runs counter to naive common sense, as bacteria are literally tiny organisms too small to see that swarm all over and inside the human body, whereas viruses are just pieces of lifeless stuff that encode information. They cannot create their own energy, like bacteria can, or translate their genetic sequences into proteins. They do not actually do anything themselves.
Viruses are just bad news wrapped in protein, as the Nobel prize winning British biologist Sir Peter Medawar once joked.
But it is this fundamental blindness to animal passions, drives, motives, appetites and strategies that gives these infectious chemicals their terror.
Both the virus and host must constantly evolve; each time a new variant of one partner emerges to become more successful to the detriment of the other
Viruses, from the Latin for poison, are everywhere. Every drop in the ocean, for example, is full of them. They occupy every square millimetre on the human body’s exposed surfaces, like skin and mucus membranes, with plenty more inside. If there are in the order of 100 trillion cells in your body, there are more bacteria in and on it. But there are ten times as many viruses. If they were alive, they would be the dominant life form on Earth. But they are not, and it takes a calamity among the living to make viruses visible as a pestilence, often after these lifeless genetic beings have been shaped by the blind watchmaker of natural selection into new and terrifying forms.
Every organism in existence, from bacteria to whales, has viral parasites, and this is reflected in their DNA. Viruses link us in an evolutionary web. Humans are likely to have acquired all our infectious pathogens originally from wild animals, and later a few from domesticated ones. Sometimes we give them back, slightly altered.
As the scientist Michael G. Cordingley put it in his book Viruses, viruses “are remarkable engines of genetic variation that powers their own adaptive evolution and catalyzes evolutionary change in their hosts.”
They have changed us, and changed themselves in turn. Viruses are catalysts of evolution, not just for themselves, but for the life forms they infect.
“Both the virus and host must constantly evolve; each time a new variant of one partner emerges to become more successful to the detriment of the other, the other partner must equal the balance through selection of a countermeasure: punch and counterpunch,” Cordingley wrote. “In this way extraordinary and mutually complex relationships evolve between the virus and its host.”
Viruses likely first emerged just as the earliest self-replicating forms of life itself did. They may have once replicated themselves but lost the ability before finding a parasitic niche in the early biosphere. Or they may have developed novel parasitic relationships with the early genetic replicators that would later evolve into organisms. Either way, once viruses were established as parasites, natural selection was able to work on both viruses and their hosts, leading to the diverse lineages of viruses that we see today.
The combinatorial biology has been going on for billions of years. Viruses are now so diverse that there is not a single gene that they all share. Cordingley suggests that the genetic information they have created, known as the viral metagenome, “overshadows all other genetic information in the biosphere” in both volume and diversity.
In their comparatively short time on the planet, and especially in the last century, humans have helped this process along. Increasing global travel moves them around to new populations, and increasing population increases both transmission efficiency and the pace of viral evolution, simply because it leads to more instances of infection and replication, with potential for beneficial mutations each time.
For a sense of scale, consider that humans have had a few thousand generations since emerging as a species a couple of hundred thousand years ago. Any virus could have had a trillion generations over evolutionary time. Every second, for example, 10 to the power of 25 viruses infect a host bacteria on Earth, creating mutants each time. This differential, from the human perspective, is what evolutionary geneticists call Red Queen dynamics, for Lewis Carroll’s line in Through the Looking-Glass that “here, you see, it takes all the running you can do, to keep in the same place.”
Viruses evolve quicker than their hosts. This process shows its true terror in those moments when viral parasites move to new hosts, like colonists to a new world. This is what reveals them, in Cordingley’s metaphor, as lottery players with unlimited resources who buy every ticket: “if there is a winning number, they will have it.”
Viruses always win. They have nothing to lose. They are, in Cordingley’s words, “the inescapable by-products of life’s success on the planet. We owe our own evolution to them.”
The pandemic that has swept across the world and appears set for an exponential rise in Canada is a big moment in the evolutionary history of SARS-CoV-2, which until about last November was at home among bats, and which is part of a family of coronaviruses that have been shown to have infected birds and mammals for nearly 300 million years.
The response of governments has been to urge a massive behavioural adjustment on humanity. It could hardly be more drastic without causing large scale panic. Canada has suspended Parliament. Ontario has suspended new jury trials and allowed one final day of school before closing them until after March Break. New York is in a state of emergency. Masses are cancelled in Montreal. Prince Charles has cancelled a royal tour. The NBA has cancelled its season, and other sports leagues are following suit.
The whole reaction is nearly unprecedented, species wide, from amateur overuse and hoarding of facemasks to the panic buying that decimated Canadian supermarkets’ substantial toilet paper stocks.
This human behaviour is also central to the pandemic, its origin, and its future end. It spans the closing of the Russian border, China’s centrally directed autocratic shutdowns, Italy’s massive quarantine, the indulgence of conspiracy theories, and the political self-dealing of U.S. President Donald Trump, who has bounced around from dismissive nonchalance, to abruptly announcing massive travel restrictions, to sniping on Twitter at his political opponent Joe Biden about a different pandemic of a different virus a decade ago.
All of this has effects on how, if and when this virus spreads. As Prime Minister Justin Trudeau said on Friday, Canadians have the capacity to affect how this pandemic occurs.
The newly frantic attention to the crisis is a reminder that this is exactly how viruses evolved in the first place — in tandem with their hosts and the vagaries of their behaviour, from the very earliest parasitic relationships more than four billion years ago.
Change is constant. Viruses may exist for ages in the asymptomatic balance that arises between viruses and the species that act as reservoirs. Sooner or later, though, this balance is disturbed by events, often simple small ones.
For example, in the early 20th century, someone in Africa ate bushmeat from a chimpanzee and acquired a virus chimps had acquired from monkeys. A few decades later, a global pandemic of HIV became one of humanity’s greatest perils and preoccupations.
It is the same basic story this time, as a virus that exists mainly among bats arose in a market in Wuhan, perhaps by someone eating an infected animal, such as a bat or a pangolin, or by some less direct means.
It is just the opportunity the coronavirus was waiting for, if lifeless pieces of genetic information can be said to wait for opportunities.
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