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We may never have met these viruses if we hadn't threatened animals

Change their ecosystem-and something evil comes this way.

Nobody had heard of 2019nCoV before it emerged as a dangerous respiratory disease in Wuhan and it has now infected about 60,000 people in China alone. It is a coronavirus similar to the Severe Acute Respiratory Syndrome (SARS) virus, akin to one prevalent in bats. 2019nCoV is a zoonosis, a disease that has jumped species.
Zonooses infect humans through contact with other vertebrate species, wild or domesticated.
2019nCoV thrives in bats. If the bat is its reservoir host, the breaking news is that the intermediate host may be the ductile and laminated pangolin, a small nocturnal mammal, slaughtered for its meat and scales. And, to clear the air immediately, there is a huge international illegal pangolin trade. The wildlife report gives a figure of 6,000 pangolins poached and smuggled out to China between 2009 and 2018 (of both varieties-the Indian Pangolin Manis crassicaudata and the Chinese Pangolin Manis pentadactyla).
Even if we aren't sure that the pangolin should take the blame, this is illustrative of how a viral disease emerges.
Many recent killer diseases are zoonoses. These are caused by viruses, bacteria, protozoa-and even prions. We've known about them for millennia. Rabies? Smallpox? Plague?
More modern horrors-HIV, Ebola, SARS, Avian Flu, Zika Congenital Syndrome, and now, 2019nCoV.
What about the diseases so part of our landscape that we simply endure them?
Dengue. Chikungunya. Japanese Encephalitis. Malaria. Don't get me started, please.
All these are illnesses we desperately try to cure, control or contain. We look upon this muscular effort as the conquest of disease. It is time we lost this rhetoric and got real.
We've 'conquered' not one of these diseases. And we have no idea, none at all, what peril is likely to hit us next. It might be nothing worse than a mild rash. Or, it could be a nightmare like Zika Congenital Syndrome.
It is time we realised the truth about what's happening. When a killer disease emerges, we're being shown our place in the web of life.
Yes, we have pushed a million species to the verge of extinction, but we're not quite the lords of creation we imagine ourselves to be. A couple more pandemics down the line and-pouf!-count us among that missing million.
Older, long familiar, zoonoses usually infected us from domesticated animals and birds. Recent zoonoses are increasingly sourced from wildlife. It is time for détente.
Viruses are everywhere in nature. They inhabit us too, by the trillion. They cannot be conquered or eliminated or even controlled. We don't even know how many viruses are capable of infecting us, or even where they hide. We stumble over pixels of information when an illness emerges, and with a bit of smart detective work, a few pieces of the jigsaw may fall in place.
Viruses need a host to replicate, disperse and circulate. They occupy the host cell and sabotage its machinery: use up its energy, garble messenger proteins, even subvert its DNA. The host organism signs in sick either because of specific organs being viral targets, or more subtly and disastrously, because its defence systems fold up.
Viruses exist in nature in a reservoir host. They may cause sporadic illnesses, but continue to pool in this reservoir population, until this balance is disturbed by environmental change. The reservoir host is threatened, the virus seeks better opportunity elsewhere, and makes a species jump.
The Anthropocene, this eon we inhabit, is moulded and defined by the human presence everywhere. As we encroach on habitats, we impose dictatorships over their populations. If that sounds paranoid, ask yourself how many individuals does a tree contain? A single tree contains thousands. Trillions when you grant personhood to microbes. Their hosts are animals, birds, insects-and the tree itself.
Extend this to cover a patch of land as big as the street where you live.
Now think of a forest.
Maths fails you?
Right.
Now think of Kyasanur Forest Disease. Yellow Fever. Dengue. Chikungunya. Zika Fever.
Let's look at the recent past. Since 1980, novel human pathogens have emerged at the rate of three per year. Three-fourths of these have been viruses. (Not all of them are dangerous enough for panic.) And, putting an end to scientific racism, these new viruses have popped up all over the planet-except Antarctica.
Most of these viruses circulate in mammals, and some in birds.
Rodents are our close relatives. Bats, ungulates, carnivores-are all familiar faces, but even long-lost cousins have begun to show up in the family album of host species.
Change their ecosystem-and something evil comes this way.
Intensification of human activity and encroachment of habitat disturb ecosystems we didn't even suspect existed.
The degree of contact between humans and wild species-or between domesticated and wild species-increases everywhere, and all the time. This means more than mere propinquity. It means transmission of microbes through various routes: aerosols that can be inhaled, faecal particles that can be swallowed, and, commonest of all, vectors like ticks and mosquitoes that can inject viruses directly into our blood.
Will such microbes inevitably infect us?
The closer to our own species the host is, the more certain this seems to be.
Invertebrates haven't contributed, yet. Neither have plants. We don't know enough about the species barrier to laugh this off.
But it is common sense that infection depends much upon the human response-and our vulnerability can be immunological or genetic. And, most importantly, nutritional.
Will the infection spread? Can it be transmitted from one person to another? Will I get it? These are vital questions that measure an epidemic. Barriers to transmission-isolation and quarantine-don't always work. Neither does shunning and brute force.
Infections often increase in both number and virulence within the isolated population.
Viruses evolve very rapidly, which is why Nipah, Ebola, SARS, and now 2019nCoV, are killers.
We may never have met these viruses if we hadn't threatened their hosts. With more than a thousand dead, isn't it time we eased off the pangolin and made détente with the bat?
- The Open magazine
- Kalpish Ratna is a writer based in India.