Expert explains: getting out of the Covid-19 pandemic, seeing viruses in perspective
Over the past couple of years, viruses have had a bad press. They have been cataloged as evil and detrimental to our existence. On the other hand, we projected ourselves as innocent victims of their cruelty.
We are led to believe that viruses exist primarily to harm us. If we could, we’d confer a bunch of Nobel Prizes (medicine, economics, chemistry, and peace) on anyone who accomplishes total virus annihilation. This, however, would be a fatal mistake – far deadlier than any potential variant of Sars-CoV2 or even Ebola.
Barraged as we have been about the invasion of a virus and its mutant strains, it’s easy to ignore that our planet harbors about 10 nonillion viruses (10 to the power of 31), enough to give one to every star of the universe 100 million time is over. In comparison, we are less than 8 billion. We occupy a microscopic space in their midst and they generally tolerate our presence until we start to behave like unpleasant guests.
Viruses existed on Earth for 3.5 billion years before humans. They permeate all parts of the natural world, hiding in soil, seawater and drifting through the atmosphere. Almost all of them are harmless to humans and many perform important functions in maintaining our ecosystem. Only 219 of the approximately 1.7 million viral species in mammals and birds infect humans. Others deal with the health of specific organisms such as fungi, plants, insects and even humans.
Bacteriophages, often simply called phages, are viruses that infect and kill bacteria. In the ocean, phages are the most important regulators of bacterial populations. They allow the microbial creatures that produce half of the world’s oxygen to survive in the ocean.
Phages are present in the mucous membranes of our digestive, respiratory and reproductive tracts and function as barriers against invading bacteria, thus preventing infection and aiding our survival.
Viruses that help and protect
For nearly a century, phages have been used to treat sepsis caused by deadly bacteria. These viruses have been isolated from bodies of water, dirt, air, sewage, and even the bodily fluids of patients. Today, there is renewed interest in the use of genetically modified phages, particularly in the treatment of drug-resistant infections.
Viruses, such as latent herpes virus and Pegivirus C, when present in our body, protect us from their dangerous cousins. The antigens produced by the latent herpes virus help the immune system identify and target cancer cells. Pigivirus C, often called GBV-C, is a virus that causes no symptoms. Several studies have shown that HIV and Ebola patients who are infected with GBV-C live longer than those who are not. By inhibiting host receptors essential for entry into cells, GBV-C slows disease and enhances the release of antiviral interferons and cytokines.
More importantly, viruses have played a vital role in the evolution of our species. We might never have existed without them! Viruses have been infiltrating human genomes for hundreds of millions of years. Their genetic material represents about 8% of the human genome.
Some viral genes produce proteins like syntectin which allows the fetus to fuse with the mother through the placenta, but for which the embryo would die. Furthermore, retroviruses have played a role in the evolution of the mammalian placenta. Stanford researchers believe that HERVK (Human Endogenous Retrovirus K), which has been embedded in human DNA for over 200,000 years, protects the embryo from further viral infections.
Three hundred and eighty trillion viruses reside on and inside the human body, more than 10 times the number of bacteria. They infiltrate all parts of the body, including the blood, cerebrospinal fluid, organs, and skin. If a minority of them can be harmful to us, most of them coexist with us and many even facilitate our survival.
We should marvel at the ability of viruses to coexist with our cells, bacteria and other viruses in habitats as diverse as the oceans and the human gastrointestinal tract. They prevent any particular microbe from becoming dominant, much like predatory animals control prey populations. When populations become too dense, viruses reproduce quickly and adjust numbers, making room for all species to thrive.
When humans trigger viruses
Frequent contact between humans and animals, usually through human intrusion into their habitats, increases the risk of zoonotic viral transmission. Forest degradation for urban development, mining, hunting, animal slaughter, as well as the global animal trade have been major drivers for the spread of the virus.
A 2017 study published in the journal Science suggests that nearly half of the world’s species are already on the move due to rising temperatures and changing rainfall patterns. According to the Lancet Countdown 2019 report, climate change has facilitated the spread of many diseases, putting increasing numbers of people at risk. Population growth, climate change and high rates of greenhouse gas (GHG) emissions are all expected to increase the number of Ebola-prone areas by 20-30%. Ebola could, on average, break out once every 10 years by 2070, rising from the current average of 17 years.
When land animals migrate, they carry their viruses and transmit them. If humans invade their territories or cross their path, new possibilities for pandemics emerge. If no action is taken to combat climate change, an estimated one billion people could be exposed to mosquito-borne diseases for the first time by 2080.
A perspective for the future
The Covid-19 pandemic is the result of the unfortunate but avoidable confluence of disease-spreading ecological factors. There is a reason why pandemics happen. The size of the host population and its degree of environmental disturbance are major factors in the emergence of pandemics. According to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), humans have significantly altered three-quarters of Earth’s land and two-thirds of its oceans.
As wildlife shifts its distribution in response to human activity, disease spreads will continue to occur across the planet. Two-thirds of human infectious diseases and three-quarters of new emerging diseases are caused by animal fallout. Wild mammals and birds have many zoonotic viruses to transmit to us. We are playing a deadly game of viral roulette when we irresponsibly engage with other species.
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Scientists have only recently begun to examine and therefore find ways in which viruses sustain all life. As we move away from the pandemic, we must ensure safe and sustainable coexistence with other species. Ultimately, the more we learn about viruses, the more willing we will be to use some of them for our good. We will also prepare for those that could lead to the next pandemic.
We became the dominant species on Earth following the annihilation of other previously dominant species. It could be our turn to have us snatch the baton. We have manipulated ecosystems for decades at great risk to ourselves and our planet. Ultimately, nature and viruses will decide how long we can all coexist. In the meantime, humility in acknowledging our guest status on our planet might be the best vaccine to ensure our survival.