Many environmental reporters and researchers maintain a keen interest in what are called “zoonotic diseases,” that is, diseases that are common in one species, like a mouse or a bat, but which for some reason jump into another one, especially ours. AIDS, Lyme, West Nile, they are all this class of disease, and the reason ecologists and environmentalists study them is that, as Peter Dasak, a disease ecologist quoted in a recent New York Times article, says, “Any emerging disease in the last 30 or 40 years has come about as a result of encroachment into wild lands and changes in demography.” In other words, if too many people go into wild areas and disturb the balance between animals, plants and their natural microorganisms, new diseases will result. Add the human tendency to jump on airplanes and travel around the world, and we begin to understand how a camel or bat virus from Saudi Arabia or China can end up in the Chateauguay Valley. This is why ecologists support more controls and precautions being put onto influxes of humans into wild places.
A new virus that’s mutated so it can, for the first time, make a living in humans, is a bit like your pet farm cat being suddenly transported to an island full of ground-nesting birds and lizards. On the farm, cats kill birds and mice, but a balance is maintained because the kitties have other food resources (like kibble) and local predators, like coyotes. In a brand-new habitat, like an island, even the simple house cat, with defenseless organisms to feed on, freedom to multiply and no predators, can exterminate entire species in very short order, sickening or even killing off the healthy balance of life the area once enjoyed. This can happen to a degree that even the cats may eventually starve, once all that food is gone.
In the case of COVID-19, the cat is a metaphor for this virus, formerly existing rather peaceably (researchers think) in bats. The cultural practice in China of regarding wild species as food and medicine likely brought infected species to the wild markets in Wuhan, where, mixing intimately with humans and other animals there, like the pangolin, the virus was able to mutate and then jump into us. In contrast with the common cold, also a coronavirus, we have no defences against it, which is why it’s also called “novel.”
Scientists believe SARS and Ebola also originated in bats. The first was likely passed to us through the practice of humans invading jungles to eat wild civet cats. The most recent Ebola epidemic, finishing only two years ago, has been traced by researchers to international fish trawlers that decimated the fish along the African coast for sale in Europe. In search of protein, the local Africans, who had depended on that catch, penetrated the forests, handily opened up to them by a government in search of money from logging. Living in these wild areas brought them in close contact with bats and, hence, Ebola. It was camels, however, that likely transmitted Middle East Respiratory Syndrome (MERS), another coronavirus.
Some medical researchers are pointing out that we’re lucky that COVID-19 is relatively mild, and this is true. Other zoonotic diseases include bubonic plague and cholera; they can be transmitted through the air and have much higher death rates. In fact, more dangerous diseases like Marburg HF and Ebola often tend to self control because, like rapacious cats, they can kill so many of their hosts that in effect, they run out of habitat and burn out. COVID-19 is also milder than SARS or MERS, with, so far, a mortality rate of only two to six percent, compared with 10 and 35 percent for the other two.
However, “relative mildness” doesn’t mean our health experts are over-reacting. Because it spreads exponentially and mostly because it’s a novel virus, in a new habitat for the first time (our bodies), it’s impossible for experts to predict exactly what it will do. For example, they don’t know whether it will maintain this same rate, die down gradually, mutate to something more alarming, or linger, flaring up in other ways. A vaccine is a breakthrough that will take months, because only time will allow the testing necessary to assess if it actually works. Until and if there is one (there are still no completely reliable vaccines for many coronaviruses), the only defence is the one we’re now following: slowing the rate of infection, so that our health system is able to treat people and save as many of the most vulnerable as possible.
So, as you sit at home with your kids (or your cat), the chart accompanying this story can help keep the situation in proportion. It works both ways: it could be a lot worse; but still, there’s a very good reason you’re not at work today, and you shouldn’t break those rules of social distancing unless you absolutely have to!
