Back in the 1990s, in the days when I still had time to pursue sidetracks, I did a remote history course. Never completed it because work broke in on it. However I did write an essay on zoonotic diseases and their effect on history and implications for the modern world of air-travel. So covid-19 came as no surprise to me.
About the only thing that surprised me was that it took so long for a pandemic to really break out into the human world. Because our evolutionary and recorded history is mainly punctuated and constrained by disease and environmental change. We invented large cities many times in the past and lost them to plague or drought. It looks like we’re going through that phase again – just at a large level.
There is a great piece over at The New York Times that runs through this in reasonable detail “How Humanity Unleashed a Flood of New Diseases“. The first part is a bit of a reconstruction. But the authors start getting into the meat of it when they describe what the disease process in the backlands of human society. I’ve highlighted in italics, what I suspect was the difference between covid-19 and its close cousin SARS.
There is much we don’t know about the origins of the ongoing pandemic and some details that we may never learn. Though genetic sequencing currently indicates that horseshoe bats are the ultimate source of SARS-CoV-2, it’s possible another animal will eventually prove to be the vector. Bats may have initially infected livestock or more exotic captive creatures raised on one of China’s many wildlife farms. Perhaps the bats (or another vector) were smuggled across the southern border from a neighboring country, like Myanmar or Vietnam. Or maybe the virus was intermittently infecting animals and people in rural areas for years before finally finding a route to a major city. Regardless of SARS-CoV-2’s precise trajectory, experts agree that Covid-19 is a zoonosis, a disease that jumped from animals to humans.
The market in the cities is the end of the journey that probably started much earlier. Viruses aren’t there to make a fuss about killing or making people sick. Their only ‘interest’ is in breeding copies of themselves. Mostly zoonotic diseases that kill are the ones that haven’t adapted to a new host well yet. The SARS outbreak in the early 2000s died because it was ill-adapted to humans – those infected appear to have almost always gotten sick at the same time that they had severe symptoms. That landed their hosts in hospitals in isolation. Covid-19 is less obvious. Most don’t get severe symptoms, and infection of others typically starts before any symptoms appear.
But the reason why we’re getting an increased incidence of zoonotic diseases – well humans are largely at fault.
Zoonotic pathogens do not typically seek us out nor do they stumble onto us by pure coincidence. When diseases move from animals to humans, and vice versa, it is usually because we have reconfigured our shared ecosystems in ways that make the transition much more likely. Deforestation, mining, intensive agriculture and urban sprawl destroy natural habitats, forcing wild creatures to venture into human communities. Excessive hunting, trade and consumption of wildlife significantly increase the probability of cross-species infection. Modern transportation can disperse dangerous microbes across the world in a matter of hours. “Human-caused ecological pressures and disruptions are bringing animal pathogens ever more into contact with human populations,” David Quammen wrote in his 2012 book “Spillover,” “while human technology and behavior are spreading those pathogens ever more widely and quickly.”
The NYT article goes at great length about this. But clearly the real issue for humans is how to prevent the next outbreak. Because we will get more. At present we’re getting these zoonotic diseases in severe outbreaks every decade, and it is likely that the rate will increase over time and as the habitats get smaller for diseases in wildlife. And of course some specific human behaviours are outright dangerous from the viewpoint of disease prevention.
Eliminating zoonoses is effectively impossible. Our survival depends on an intricate web of connections to other living creatures, including micro-organisms. We cannot sanitize the planet or live in hermetically sealed bubbles. We cannot prevent new viruses from emerging. But we can significantly reduce the risk of dangerous pathogens spilling from animals into human populations. In the wake of SARS and the early stages of Covid-19, the most obvious target for reform is the wildlife trade.
The wildlife trade is an ecological aberration: It thrusts species that would otherwise never meet into strained intimacy. Because captive animals are often undernourished and stressed, they are more susceptible to infection. When they are butchered on the spot, which happens in certain live-animal markets, their bespattered fluids potentially expose other animals as well as humans. It’s an unparalleled crossroads for infectious pathogens. Urbanization, increasing affluence and improved infrastructure, such as new roads into formerly inaccessible wilderness, have bolstered the expansion and commercialization of the live-animal trade around the world.
Of course, in some cases, people depend on wildlife for sustenance. Some 150 million households in Latin America, Asia and Africa hunt wild animals, primarily for personal consumption, according to a 2017 estimate; poorer households tend to rely most strongly on wild meat. Among the middle and upper classes of China’s growing urban population, the trend of eating wild creatures has less to do with survival than status: a way to signal wealth and honor guests. According to another 2017 study, meat consumption in China has increased by a third since 2000, more rapidly than in any other major economy, and demand for wildlife products of all kinds has surged. Exotic meat has appeal in the West, too: Many thousands of pounds of bush meat — primates, antelope, rodents, birds and reptiles — are smuggled into Europe and North America every year. In the United States, 11.5 million people hunt and sometimes eat animals such as deer, elk, moose, bears, raccoons, porcupines, doves, quail, pheasants, armadillos, squirrels and alligators.
As they conclude..
Ultimately, the prevention of zoonoses demands more than practical interventions; it requires a fundamental shift in perspective. Humans have a long history of treating the world as our stage and other creatures as our props. We pluck rare orchids from remote swamps and ship them halfway around the world, not because we need them but simply because we like the way they look on our windowsills. We kill wild tigers out of fear or for sport and simultaneously breed them in captivity so we can cart mewling cubs to petting zoos and mall photo shoots. Wherever we settle, we eradicate native species and replace them with organisms entirely unfamiliar to that ecosystem. When one of our accidental introductions becomes too problematic to ignore, we often import yet another exotic creature to defeat the first — a strategy that has repeatedly and spectacularly failed.
More than any other entity, viruses and microorganisms expose the fallacy of our tyrannical choreography. We are used to thinking of ourselves as the protagonists of every landscape, but from the perspective of infectious microbes, we and other large creatures are the landscape. As we restructure Earth’s biosphere to suit our whims, we open hidden conduits between other animals’ microbiomes and our own. Once those channels are in place, pathogens can no more stop themselves from spilling into us than water can prevent itself from running downhill. We cannot blame the bats, mosquitoes and viruses. We cannot expect them to go against their nature. The challenge before us is how best to govern ourselves and stymie the flood we unleashed.
Definitely worth reading. Because we’re going to do another covid-19 style pandemic to ourselves again, unless we change what we do to the rest of the biosphere that we all live in.