More on this book
Community
Kindle Notes & Highlights
Read between
September 26 - December 25, 2020
humanity is a kind of animal, inextricably connected with other animals: in origin and in descent, in sickness and in health.
INFECTIOUS DISEASE IS all around us. Infectious disease is a kind of natural mortar binding one creature to another, one species to another, within the elaborate biophysical edifices we call ecosystems.
This form of interspecies leap is common, not rare; about 60 percent of all human infectious diseases currently known either cross routinely or have recently crossed between other animals and us.
Zoonotic pathogens can hide. That’s what makes them so interesting, so complicated, and so problematic.
A reservoir host (some scientists prefer “natural host”) is a living organism that carries the pathogen, harbors it chronically, while suffering little or no illness.
To reside undetected within a reservoir host is probably easiest wherever biological diversity is high and the ecosystem is relatively undisturbed. The converse is also true: Ecological disturbance causes diseases to emerge. Shake a tree, and things fall out.
Nearly all zoonotic diseases result from infection by one of six kinds of pathogen: viruses, bacteria, fungi, protists (a group of small, complex creatures such as amoebae, formerly but misleadingly known as protozoans), prions, and worms.
Viruses are the most problematic. They evolve quickly, they are unaffected by antibiotics, they can be elusive, they can be versatile, they can inflict extremely high rates of fatality, and they are fiendishly simple, at least relative to other living or quasi-living creatures.
“Viruses have no locomotion,”1 according to the eminent virologist Stephen S. Morse, “yet many of them have traveled around the world.” They can’t run, they can’t walk, they can’t swim, they can’t crawl. They ride.
An amplifier host is a creature in which a virus or other pathogen replicates—and from which it spews—with extraordinary abundance.
Not every zoonotic pathogen requires an amplifier host for successful infection of humans, but some evidently do.
Make no mistake, they are connected, these disease outbreaks coming one after another. And they are not simply happening to us; they represent the unintended results of things we are doing. They reflect the convergence of two forms of crisis on our planet. The first crisis is ecological, the second is medical. As the two intersect, their joint consequences appear as a pattern of weird and terrible new diseases, emerging from unexpected sources and raising deep concern, deep foreboding, among the scientists who study them.
Human-caused ecological pressures and disruptions are bringing animal pathogens ever more into contact with human populations, while human technology and behavior are spreading those pathogens ever more widely and quickly.
“Spillover” is the term used by disease ecologists (it has a different use for economists) to denote the moment when a pathogen passes from members of one species, as host, into members of another.
Why do strange new diseases emerge when they do, where they do, as they do, and not elsewhere, other ways, at other times? Is it happening more now than in the past? If so, how are we bringing these afflictions upon ourselves?
People and gorillas, horses and duikers and pigs, monkeys and chimps and bats and viruses: We’re all in this together.
Another implication was that epidemics don’t end because all the susceptible individuals are either dead or recovered. They end because susceptible individuals are no longer sufficiently dense within the population.
the average number of secondary infections produced, at the beginning of an outbreak, when one infected individual enters a population where all individuals are nonimmune and therefore susceptible. MacDonald had identified a crucial index—fateful, determinative. If the basic reproduction rate was less than 1, the disease fizzled away. If it was greater than 1 (greater than 1.0, to be more precise), the outbreak grew. And if it was considerably greater than 1.0, then kaboom: an epidemic.
They were right, and the virus became known as SARS coronavirus, inelegantly abbreviated as SARS-CoV. It was the first coronavirus ever found to inflict serious illness upon humans.
The much darker story remains to be told, probably not about this virus but about another. When the Next Big One comes, we can guess, it will likely conform to the same perverse pattern, high infectivity preceding notable symptoms. That will help it to move through cities and airports like an angel of death.
well he certainly got this right!
Kirsty liked this
THE NEXT BIG One, as I mentioned at the start of this book, is a subject that disease scientists around the world often address. They think about it, they talk about it, and they’re quite accustomed to being asked about it. As they do their work or discuss pandemics of the past, the Next Big One (NBO) is at the back of their minds.
Moral: If you’re a thriving population, living at high density but exposed to new bugs, it’s just a matter of time until the NBO arrives.
But a large fraction of all the scary new viruses I’ve mentioned so far, as well as others I haven’t mentioned, come jumping at us from bats.
Hendra: from bats. Marburg: from bats. SARS-CoV: from bats.
Just before pulling his own mask into place, Epstein noted cheerily: “With new and emerging viruses, it’s all about prevention. Once you have the virus, there’s not much you can do.”
If bats are so abundant and diverse and mobile, and zoonotic viruses so common within them, why don’t those viruses spill into humans and take hold more frequently? Is there some mystical umbrella that protects us? Or is it fool’s luck?
Yes, we are all gonna die. Yes. We are all gonna pay taxes and we are all gonna die. Most of us, though, will probably die of something more mundane than a new virus lately emerged from a duck or a chimpanzee or a bat.
Whatever happens after that will depend on science, politics, social mores, public opinion, public will, and other forms of human behavior. It will depend on how we citizens respond.
That’s the salubrious thing about zoonotic diseases: They remind us, as St. Francis did, that we humans are inseparable from the natural world. In fact, there is no “natural world,” it’s a bad and artificial phrase. There is only the world. Humankind is part of that world, as are the ebolaviruses, as are the influenzas and the HIVs, as are Nipah and Hendra and SARS, as are chimpanzees and bats and palm civets and bar-headed geese, as is the next murderous virus—the one we haven’t yet detected.
