By Ian Angus
Part Two of a multi-part article on the causes and implications of global capitalism’s descent into an era when infectious diseases are ever more common. My views are subject to continuing debate and testing in practice. I look forward to your comments, criticisms, and corrections. Read part one.
A question that goes unasked in most accounts of the COVID-19 pandemic is why now? Why has a virus that for centuries resided peacefully in a wild animal in rural China suddenly attacked millions of humans around the world?
For a potentially deadly virus to cause actual disease, conditions must exist for it to infect a plant or animal and multiply. And for a disease to become an epidemic or pandemic, conditions must exist for it to spread rapidly to others. Epidemics and pandemics are simultaneously micro-biological and macro-ecological—they emerge and spread through interaction and conflict between biological change and social change.
To understand why new viral diseases are multiplying now, we focus first on the relentless evolution of Earth’s smallest and most numerous biological entities.
If you ask most people what viruses are, they’ll say something about germs and disease. Indeed, until recently that was how most scientists viewed them: in 1977 the famous biologists Jean and Peter Medawar wrote that a virus is “simply a piece of bad news wrapped up in protein.” No one could see a virus before the invention of the electron microscope in the 1930s, and unless it caused disease, scientists didn’t know to look for it. For decades, viruses were classified by their appearance and their impact on human health.
Only in this century has automated genetic analysis enabled the rapid identification of large numbers of viruses, causing a revolution in virology. In study after study, scientists are discovering thousands of previously-unknown viruses at a time—so many that efforts to catalog them have trouble keeping up, and we have no idea what (if anything) most of them do.
The figures are mind-boggling. Can anyone truly grasp numbers like the estimated 1031 individual viruses on Earth—10 million times as many as there are stars in the universe? Every liter of ocean water contains about 100 billion viruses, and wind-borne dust carries some 800 million viruses to every square meter of the earth’s surface, every day. There are about a trillion viruses in your body at any given time—some infect your human cells, some infect the millions of bacteria we all carry, and some are just passing through on your food or breath.
They are, as evolutionary biologist John Thompson writes,
in many ways the most successful lifestyle on earth.”
Viruses are, by far, the most abundant organic entities we know of; in fact, they are probably more common than all other forms of life combined… Every ecological niche in which life can be found has been penetrated by the virosphere. Over 100 million types of viruses infect all species of living beings, including animals, microbes, and plants.
Most viruses are specialists that can only infect particular species of microbes, plants, or animals—and usually only specific kinds of cells in specific species. Rabies, for example, initially infects muscle cells of some mammals, then attacks their brain cells. Ebola viruses target cells in human livers and immune systems, and the linings of our veins and arteries. Coronaviruses infect cells in human respiratory tracts, some causing mild cold symptoms and others causing SARS or COVID-19.
Viruses play major roles in the biogeochemical cycles that define and drive the entire Earth System. Some viruses kill billions of single-celled organisms in the oceans every day, sinking (and eventually recycling) millions of tons of organic carbon. About one-quarter of fixed carbon passes through such virus-driven processes, and five percent of the oxygen you breathe comes from virus-stimulated photosynthesis in the oceans. Many viruses co-exist in permanent symbiotic relationships inside the cells of plants and animals, killing harmful bacteria, stimulating production of essential chemicals, aiding digestion, and much more. About 8% of the human genome is DNA that originally came from various viruses.
But in this article I focus on the small minority, a fraction of a percent of all virus species, that can cause disease in humans and other animals. Two biological characteristics, common to all viruses, make these potential pathogens particularly dangerous.
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