Example essay

GUEST ESSAY: Emerging infectious diseases and climate change | Columnists


At the farmer’s market a few Saturdays ago, a woman I vaguely recognized but couldn’t place greeted me warmly. She saw my hesitation and explained to me that I had treated her for Lyme disease in the 1980s, with success.

“Wow,” I say. ” It was a long time ago. How did you recognize me at my now advanced age?

Turns out she’s reading The Post Star, just like you, and I had seen my Earth Day essay and picture. So we caught up a bit, stopping to applaud the fiddlers when they finished the song.

“I have to ask you, because in this essay you asked me to ask,” she said. “Why are all these new germs emerging, like Ebola, SARS and COVID-19, and how is their emergence related to global warming?”

“Oh, boy,” I said, “it’s complicated. Let me write an essay.

Germs are smart

Germs, i.e. fungi, bacteria and viruses, are incredibly intelligent. Not smart like us, of course… but maybe smarter. They were, after all, here at the very beginning of life. Over these eons, they have learned four brilliant strategies for surviving and reproducing in this harsh world, strategies that will certainly allow them to outlast our race for a long time.

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The first strategy is self-replication, the necessary prerequisite for life. Germs amplify this strategy by reproducing very, very quickly – vastly faster than animals.

A second is genetic mutation. Mutations occur spontaneously when living things reproduce. Most mutations do not give advantage to the life form. But some do, and sometimes a mutation will provide the organism with a much better ability to survive and thrive. Because germs reproduce so quickly, they arrive at favorable mutations about 1.753 billion times faster than humans.

The third is to capture the energy to fuel their life and reproduction. Different types of sprouts do this in different, but still effective ways. Ingeniously, viruses move into a cell of another life form, a host. They then avoid a pile of work by turning that host cell into a factory to replicate hordes of new viruses. SARS-CoV-2, the cause of COVID-19, does it in our noses and throats. In contrast, people are mindlessly chopping down forests and jungles, the lungs of our planet, to create ranches for cattle belching methane and thus food for our bellies. Maybe there is a more inefficient way to harness energy than ours, but I can’t think of it right now.

The fourth strategy, designed so that germs can spread through a group of hosts, is mobility. Since they cannot move on their own, they depend on being transported by something else. Hepatitis A and noroviruses, for example, are waterborne. They start in one host’s digestive track, poop in water, and, sorry to say, go back into another host’s mouth. Some germs travel when animals rub against each other – Ebola, monkeypox or human papilloma virus. Or bite each other – rabies. Measles, chickenpox, influenza and coronaviruses travel through the air, launched by sneezes or coughs and carried by breezes to another nose or throat.

There is a fifth factor, which is not a germline strategy: it is the environment in which the germ has found it can exist. In fact, the recently emerged viruses, HIV/AIDS, monkeypox, Ebola, Marburg, and SARS-CoV-2, have existed for decades or centuries in specific environmental niches, hidden from our eyes in primates and bats. Then came delightful changes to the environment that made breeding and travel much easier. Changes like cutting down forests to make room for more farm animals and people. Or changes like the terrible overcrowding of refugees in very unsanitary camps. Can you imagine what would happen if Ebola was introduced into a Syrian refugee camp in Greece, where the dirt would be the worst possible?


The coronavirus family is a huge family, which probably evolved from a common ancestor millions of years ago. Subspecies of the family have tended to thrive in dozens of different types of bats, especially in China. Some have interbred with other animals; for example, four different strains have long been circulating in humans, causing some of our common colds. Then in Wuhan, China, in 2003, a strain emerged from bats, jumped into mammals called civets, and then into humans, causing the first SARS pandemic; it was SARS-CoV-1. The SARS-CoV-2 pandemic, from which we have all suffered so much over the past two years, almost certainly started the same way, moving from similar Chinese bats to another animal host, then to us.

China is a country of 1.3 billion people, most of whom are crammed into densely populated cities, cities that have grown rapidly, spreading over what was once land used for agriculture or were wild. Invasion and destruction of animal habitat resulted. Animals and humans have collided with bats, allowing SARS-CoV-2 to travel through the air or through direct contact across species lineages. Once installed in the respiratory tract of a few people, the virus was delighted to rush into an ecological niche unprecedented for them, a tight city. All cities are connected by land and air, of course. You know the rest.

The role of climate change

The harsh reality is that we humans are burning our fossil fuels and heating the planet more and more. All things that live and can move seek out lands that are still habitable—generally higher lands away from rising seas, lands with usable water, lands where the temperatures are still bearable.

A groundbreaking new analysis, called the “Iceberg Study”, has just been published in the journal, Nature. The authors, Albury and Carlson, showed that due to widespread global warming and more localized climatic disturbances such as droughts or wildfires, animals that have been content for centuries with specific ecosystems are forced to move towards new habitats to find their preferred environment. conditions. Each migrating animal naturally brings its resident viruses. As species that hadn’t come into contact before now collide with each other, their viruses can jump.

Albury and Carlson mapped the past, present, and likely future ranges of more than 3,000 mammals as they have moved and are likely to move. Based on this mapping, the authors estimate that over the next few decades about 300,000 new species encounters will occur, and about 15,000 virus spillovers onto new hosts will also occur. What we’ve experienced as a slew of alarming emerging infectious diseases is, they believe, just the tip of the iceberg we’re up against.

Many of these species encounters and resulting viral transfers have happened and will continue to happen in Africa (think Ebola) and Southeast Asia (think coronavirus). Why? Bats. For several reasons. Bat populations tend to harbor many nasty viruses, oddly enough without getting sick themselves. And bats react more quickly to climatic pressures than other mammals because they can fly and move faster. In Africa and Southeast Asia, there are many subspecies of bats, each with its own territory and resident viral cohabitants. Bats and people are all heading to the remaining more climate-friendly places.

But don’t just blame the bats. HIV had long lived in chimpanzees in the jungles of the Congo, but jumped to people in the early 20th century. Similarly, the main reservoirs of monkeypox are rodents, rats and squirrels, which also live in the Congo Basin. It was, of course, humans who invaded and slaughtered the jungles, inviting these viral transfers.

To finish

Thus, we are beginning to understand that emerging infectious diseases are not random events. They happen because microbes are so inventive at taking advantage of their situation. When they find a more comfortable and nurturing environment, they throw a party. We are also becoming aware that we humans are damaging the Earth in ways that germs can celebrate.

All of this is happening now. As our planet warms and more species collide, chances are we will experience more infections and emerging pandemics. If humans are really smart – which I’m not so sure about – we’ll be looking at all of this carefully and being very worried, especially with COVID-19 still hitting us. And we’ll decide that we really don’t want any more.

There are ways to change the odds, ways already understood and others imagined by those who are aware of what is happening. I’m too tired to list them all. But one obvious way is to stop destroying forests and jungles. And you know very well that the first way you and I can personally address is to stop burning down our only home.

Please live wisely and be well.

Richard Leach, MD, is a retired internist, infectious disease consultant, and travel and tropical medicine specialist. He practiced in Glens Falls for 35 years, as an infection control officer and hospital epidemiologist at Glens Falls Hospital.

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