The Emergence of Severe Acute Respiratory Syndrome (SARS)

“The message we are getting is if we don’t take care of nature, it will take care of us.” — Elizabeth Maruma Mrema, Acting UN Executive Secretary on the Convention on Biological Diversity.

“It boggles my mind how, when we have so many diseases that emanate out of that unusual human-animal interface, that we don’t just shut it down. I don’t know what else has to happen to get us to appreciate that.” — Dr. Anthony Fauci on live animal markets, aka wet markets, in Asia and elsewhere. 

“The term wet market is often used to signify a live animal market that slaughters animals upon customer purchase.” — X. F. Xan

“This is a serious animal welfare problem, by any measure. But it is also an extremely serious public health concern.” — Kitty Block, President and CEO of the Humane Society of the United States.


As we come closer to the present time, to the present COVID-19 Climate of Pandemic, we run into illnesses that are more mysterious. HIV, for example, has been the object of intense investigation and scrutiny for many decades now. So the level of knowledge about how HIV emerged is quite rich. Less so with Ebola, but that infection is still moderately well understood.

SARS — Another Novel Illness

With the newer SARS illness — short for severe acute respiratory syndrome, the well of scientific understanding from which we can draw is far more shallow. But it is certainly relevant. For the present global pandemic which now has paralyzed our entire civilization and which threatens to take so many of our lives resulted from the second strain of human SARS to emerge in our world.

What we do know is that the SARS virus is another new zoonotic illness. The first strain of SARS broke out in a 2002 epidemic in China that then rapidly spread. It emerged from a family of coronaviruses. A set of viruses that typically cause mild respiratory infections in humans. But SARS virus is not mild. It is quite often severe — resulting in hospitalization in a high proportion of cases. It also shows a much higher lethality rate than typical illness.

SARS comes from a lineage, like HIV and Ebola, that had previously thrived in the hotter regions of the globe. It was harbored in tropical and subtropical animal reservoirs. It emerged at a time when animal sicknesses were likely amplified by direct environmental stresses caused by forest clear cutting, human encroachment, and the broader sting inflicted by the climate crisis. The novel awakening of SARS was, finally, yet another case where harmful contact with sick animals resulted in a transfer of a new illness to human beings. 

Coronaviruses in Hot-Bodied Bats in a Hot Weather Region

The first strain of human SARS illness was genetically traced back to a coronavirus ancestor in horseshoe bats — a tropical and subtropical bat species — in 2002 by Chinese researchers. Like the Ebola Virus and HIV before it, SARS-like illness circulated through various species in tropical and sub-tropical environments in a traditional reservoir long before transferring to human beings.


Horseshoe bat primary range

The primary range of horseshoe bats is paleo-tropical. Horseshoe bats, according to genetic research, are an animal reservoir of SARS virus. Image source: Paleo-tropical environment.

Studies note that bats are a reservoir for a great diversity of coronaviruses. The bat anatomy is a warm one in a hot weather environment — subject to constant exercise and exertion in regions where it’s not easy to cool off. Elevated body temperature is a traditional mechanism for fighting infection. So these viruses have to constantly adapt and mutate to keep hold in the bat population.

At some point, one particular strain of coronavirus jumped out of the bat population and into another animal species. A paper in the Journal of Virology suggests that the genetic split from bat cornaviruses and SARS occurred some time around 1986 or 17 years before the 2002-2003 outbreak. At that time, it is thought that this hot weather illness from hot-bodied bats had moved to another, intermediary, animal host.

SARS in the Little Tree Cats — Palm Civets

The first emergence of SARS is thought to have occurred when palm civets — a kind of Southeast Asian tree cat — consumed coronavirus inflected horseshoe bats. The civets typically dine on tree fruits. But as omnivorous creatures they also eat small mammals. In this case, civets are thought to have eaten sick bats and become sick themselves.

The Palm Civet of Southeast Asia — hunted as bush meat for the Asian wet markets. A practice suspected for transferring SARS from bats to humans. Image source: Black Pearl, Commons.

Palm civets live throughout much Southeast Asia. Inhabiting a swath from India eastward through Thailand and Vietnam, running over to the Philippines and southward into Indonesia. A tree-dwelling creature, they prefer primary forest jungle habitats. But they are also found in secondary forests, selectively logged forests, and even parks and suburban gardens. All of which overlap the environment of horseshoe bats and their related coronavirus reservoir.

The leap from bats to civets and its development into SARS probably didn’t occur suddenly. Many civets probably consumed many sick bats over a long period of time before the coronavirus changed enough to establish itself. But at some point in the 1980s, this probably occurred.

From that point it took about 17 years for the virus to make its first leap into humans. How the virus likely made this move is eerily familiar — taking a similar route to the devastating HIV and Ebola illnesses.

Wet Markets — Butcheries For Asian Bush Meat

A major suspect for the source of this particularly harmful contact is the Chinese wet market system. A wet market is little more than a trading area that contains, among other things, live and often exotic animals for sale as food. A person entering a wet market is confronted with thousands confined live animals. They can point to a particular animal and a wet market worker will butcher the creature on the spot.

It’s literally a very bloody business. The butchering occurs in open air. Blood and body fluids can and often do splatter anywhere. As a result, the floors are typically wet from continuous drippage and, usually partial, cleaning — which is how the market derives its name.

Palm civets can often be found in wet markets as food in China. Trappers for the wet markets range the Southeast Asian jungles bringing in civets by the thousands. The civets were reservoirs for SARS virus. They were slaughtered in the messy markets. People were exposed. In 2002 and in 2019 they got sick.

Though palm civets have been identified by many avenues of research as a likely source of SARS, raccoon-dogs — whose meat was sold in wet markets — were also shown to be SARS type virus carriers. These animals have a similar diet to that of civets, share their habitat and were similarly vulnerable to infection from the bats. In addition, pangolins — a kind of scaly anteater — have been identified as a possible carrier of the SARS-CoV-2 virus. And pangolin meat is also sold for consumption in Vietnam and China.

Given our knowledge of how zoonotic illnesses move in animal populations, it’s possible that multiple species are involved in the ecology of SARS and related coronaviruses. In essence, there is a strange and ominous similarity between wet markets in Asia and the bush meat trade in Africa. They are both means of moving jungle meats from animals (who may be reservoirs for novel illnesses) in tropical regions into the human population. Often in a fashion in which the treatment and preparation of the meats to be consumed is haphazard and unregulated.

First SARS Outbreak — 2002-2003

Ultimately, the disease percolating through likely stressed natural systems found its way into the human population in late 2002. The epicenter was Guangdong Province in China where the highest proportion of early SARS cases by a significant margin (39 percent) showed up in people in the live animal food trade. In other words, people who butchered animals or worked closely with those who butchered animals.

The initial infections, which were traced back to November in China, resulted in spikes of pneumonia incidents in local hospitals. The cause — a then unknown illness that was later called SARS. SARS was another terrifying illnesses. Its symptoms could emerge rapidly or slowly over a couple of days or weeks. It could mimic flu-like symptoms before suddenly surging into a terribly lethal illness that attacked the lungs — rendering victims unable to breathe under their own power. At first, case fatality rates (the percentage of people who died as a result of SARS) ranged from 0-50 percent. The ultimate recorded fatality rate from the initial outbreak in 2002 would settle at 9.6 percent or about 100 times more lethal than seasonal flu.

SARS cases 2002 2003 outbreak

Cumulative reported SARS-CoV cases during the 2002-2003 outbreak. Note that early case reporting was incomplete. Image source: Phoenix7777 and WHO.

From the point of early infections, patients then passed on the virus to healthcare workers and others. Though SARS was not as crazy lethal as HIV and Ebola on an individual basis, it was quite infectious. Meaning it was much easier to pass on to others than either of those earlier emerging zoonotic illnesses. This higher transmission rate resulted in a greater risk that more people would fall ill from SARS over a shorter period of time — exponentially multiplying the virus’s lethal potential.

Transmission to workers in hospitals and care facilities was notable as typical sanitation procedures were not enough to limit virus spread. In hospital settings, the transmission rate for this first SARS illness (the number of people each infected person then got sick) was between 2.2 and 3.7. Outside of sanitized settings, the transmission rate ranged from 2.4 to 31.3. A particularly highly infectious patient, called a super-spreader, resulted in a mass spread of illness to workers at Sun Yat-sen Memorial Hospital in Guangzhou during January of 2003 and subsequently to other parts of China’s hospital system. Masks and protective gowns (PPE) were ultimately shown as necessary to contain SARS infection in hospitals.

China’s early failures to report on the 2002 SARS outbreak resulted in a somewhat delayed international response. But by early 2003, the World Health Organization was issuing warnings, advisories and guidance. Disease prevention agencies within countries issued their own responses including diligent contact tracing and isolation protocols. The containment response both within and outside of China was thus in full swing by early 2003. This action likely prevented a much broader pandemic. That said, a total of 8,096 cases were reported — 5,327 inside China and 2,769 in other countries. With the vast majority of cases occurring in China, Hong Kong, Taiwan, Canada, Singapore and Vietnam. In total, out of the 8,096 people reported infected during this first SARS outbreak, 774 or 9.6 percent, perished.

SARS-CoV-2 Tsunami on the Way

Unfortunately, infectious diseases show no mercy to fatigued and degraded infectious disease responses. They lurk. They mutate. In their own way, they probe our defenses. They are capable of breaking out to greater ranges when diligence, ability, or will to protect human life wanes among leaders. And a smattering of SARS cases reported during the 2000s following the 2002-2003 outbreak continued as a reminder of its potential. So as with HIV and Ebola, we face waves of illness with SARS. With the next outbreak resulting in a global pandemic that will likely infect millions and kill tens to hundreds of thousands during 2019-2020.

Up Next: COVID-19 First Outbreak — Viral Glass-Like Nodules in Lungs


From Ancient Reservoirs

“The insidious emergence of HIV/AIDS and the lack of due attention by policymakers illustrate how some outbreaks that start subtly can grow to global proportions if they are not aggressively addressed early on.” — Dr Anthony Fauci

The Infectious Diseases Society of America recognizes climate change as a global health emergency and calls for policies responding to the intrinsic links between warming temperatures and rising sea levels and epidemic and pandemic events as well as other infectious disease threats to public and individual health. — IDSA

The climate system of our world envelopes it.

It represents the state of our atmosphere, our oceans, and the frozen regions we rely on. It interacts with and influences all things living here on Earth.

The present changes we now experience due to a climate in crisis are far-reaching. Disruptive to the balance of life itself. Harmful or even demolishing to ecosystems. Driving species of all kinds into new environments after their old safe places have been changed, disrupted, or taken away.

This is a story that we have become sadly familiar with as the burning of fossil fuels keeps dumping heat-trapping carbon into our atmosphere — resulting in rising seas, melting ice, stronger storms, worsening droughts, expanding heat, and far larger and more dangerous wildfires.

Global examples of emerging infectious diseases NIH

Global examples of emerging and re-emerging infectious diseases. Even before COVID-19, they were growing more numerous. Back in the early 1990s, this map showed just one illness — HIV. To humans, quite a few are now rather new. Others are re-emerging. Many are influenced by the climate crisis in various ways. Image source: Three Decades of Responding to Disease Outbreaks — NIH.

But there is one aspect of our changing climate that is often nuanced and overlooked — how the climate crisis can influence the spread of disease itself. How a disrupted global climate can drive sickness up out of the ancient reservoirs that have harbored it throughout the ages. How it can help accelerate the spread of new illness, make us more susceptible to sickness, or cause the re-emergence of previously well-contained diseases. Given the present context of a global pandemic caused by an entirely new illness — COVID-19 — it’s crucial to take a look at generally how harmful interactions with the natural world, particularly through climate crisis, are increasing risks of new and re-emerging diseases.

Reservoirs as Illness Havens

For what we know of as illness is also a kind of life.

Bacteria are micro-organisms. Viruses are pseudo-life and life-altering. And parasites are living things that dwell within or upon other living things. Climate change can generate or worsen such illnesses by directly affecting their environments as well. Creating the conditions that facilitate the transfer of diseases from typical ranges — called reservoirs — to new hosts. Developing pathways for expanded or new (novel) infections.

An illness reservoir is any person, animal, plant, soil or substance in which an infectious agent normally lives and multiplies. A harbor for the bacteria, viruses, or parasites that cause disease.

Human beings are reservoirs for certain diseases. These could be living humans or the dead — long buried and held dormant in ancient frozen tundra for hundreds or even tens of thousands of years. It is possible that the devastating illness smallpox (Variola virus), which was recently considered eradicated, may still be harbored by frozen dead humans entombed in the permafrost. That permafrost is now thawing as the Arctic heats up.

Animals can also be reservoirs — rabies, for example, lives in bats, raccoons, skunks, and foxes. Cholera is a bacteria that lives in water. It can also live in humans and zooplankton. And there is a link between the spread of Cholera and the loss of water security — which the climate crisis risks. Anthrax lives in herd animals like sheep and reindeer. Because it is capable of developing spores, Anthrax can survive for decades in the bodies of dead reindeer and the climate crisis produced thaw of permafrost has already resulted in new outbreaks of this illness in herd animals and, in rarer possible cases, human beings. Dengue fever is a nasty virus harbored by both humans and mosquitoes. And it is worth noting for diseases which cause illness and loss of life in human beings that mosquitoes — whose range can be greatly altered by changes in climate — weigh quite heavily.

Zoonosis — The Transfer of Illness From Animals to Humans

During recent years, human beings have unfortunately seen the emergence of numerous new or novel illnesses. Many of these illnesses have arisen as the result of mistreatment of nature. Our disruption of the natural world and harmful or abusive relationships with animals appears to have done double duty in getting us ill. For a good share of the nastier new ailments have arisen as the result of zoonosis — or the transfer of diseases that previously affected only animals to human beings — involving such harmful acts.

The harmful bushmeat trade in Africa is thought to be the origin of the novel HIV virus transferring from its original reservoir in primates as SIV before mutating into a stronger illness in humans during the 20th Century to become common from the 1980s onward. Though there is little clear and present evidence that the jump from animals to humans for HIV was directly influenced by the climate crisis, the link between harmful industry and disease transfer is a bit close for comfort here. It is also worth noting that those living with HIV are among the most vulnerable to increasing extreme weather events and related disruption of human habitat and support systems driven by the climate crisis.

SARS illnesses (of which COVID-19 is a subset) and Ebola are also novel viruses in humans. As with HIV, they are likely zoonotic illnesses. This means they originated in animal host reservoirs but, through some process of contact, transferred to human beings. These viruses are still rather mysterious in that they presently have unconfirmed reservoirs. But both are reasonably suspected to be harbored by animals — with tropical and subtropical bats relatively high on the list.

With Ebola in particular (we’ll talk about some similarities between Ebola and SARS due to suspect reservoirs in the next chapter), there is a bit of an ominous interaction with the climate crisis. New modeling produced in Nature Communications suggests that under the present pathway of global heating, Ebola epidemics in Africa could occur once every 10 years — or almost twice as often as they do at present. This is because the bats and other animals that are thought to harbor the virus are expected to be driven by warming temperatures into new areas — expanding the epidemic-prone region by 20 percent.

Expanding Heat

The heating function of the climate crisis is very well understood. And, early-on, scientific research from world health and climate agencies identified the risk that more global heat posed to expanding illness. In particular, mosquitoes which are both reservoirs and vectors (agents of disease transfer) for numerous harmful illnesses are seeing their ranges greatly expand as the world heats up.

Mosquito-borne infection is an ancient and well-known threat to humankind. But it has thankfully been relegated to warmer climates. Despite knowing little about mosquito-borne Malaria, the Roman aristocrats of antiquity did know they could avoid infection by retreating to villas in the cooler hills. Away from where mosquitoes were plentiful. Unfortunately, the climate crisis is driving heat, and the mosquitoes that come with it, both uphill and into higher latitudes.

A single populous species of mosquito — Aedes aegypti — can spread four serious illnesses. They include Dengue Fever, Zika virus, Chikunyunga and Yellow Fever. As global heating continues to be driven by fossil fuel burning, the range of this mosquito is expected to greatly expand. How much depends on how rapidly we halt fossil fuel burning and transition to clean energy (or not). But a business as usual (worst case) fossil fuel burning scenario in which the clean energy transition continues to be hobbled will bring this so-called jungle fever carrier to the Arctic by the 2080s (see image above).

There are over 3,500 species of mosquito. Most are relegated to warmer climates. In addition to the illnesses mentioned above, these insects also carry Malaria and West Nile virus among many others. And as the climate heats up, their range and their ability to transfer diseases among humans will expand.

But mosquitoes are not the only disease reservoir and disease vector species now on the move as a result of the disruption caused by climate crisis. There are many. Some which we probably don’t yet know about.

Receding Cold

If tropical heat spreading northward bringing with it flights of mosquitoes and displacing other disease carriers presents one illness expansion problem, the ongoing thaw of cold regions presents another. In particular, there is evidence that the Arctic has locked away numerous ancient illnesses that could be released in the thaw produced by climate crisis.

The Variola virus which causes Smallpox may well be sequestered in the various graves and burial mounds scattered throughout the Asian and European north. A study conducted in the 1990s detected fragments of smallpox DNA in the remains of Stone Age humans as well as people who were known to have died from smallpox during the 19th Century. Though smallpox was considered eradicated from human beings, long deceased humans frozen in the Arctic may serve as a reservoir that results in potential new infections. If such a reservoir exists, the Arctic thaw produced by the climate crisis will disturb it.

Other pathogens that may still be harbored by dead humans frozen the Arctic includes the 1918 Spanish flu (H1N1) which was found in frozen regions of Alaska. In 2007, scientists discovered Spanish flu RNA in the body of an Inuit woman who’d been buried for 75 years in the permafrost.

Anthrax is a bacteria-caused infectious disease that typically afflicts herd animals such as sheep and reindeer. But Anthrax can pass to humans that are exposed to the bacteria. In 2016, 2,000 reindeer became infected with Anthrax in the Yamal Peninsula region of Siberia. Nearby, it is thought that a reindeer killed by anthrax decades before thawed out, spreading the bacteria into the lands where the reindeer grazed. These reindeer then spread the illness to a number of human beings, including a 12 year old boy who died.

The potential for the release of both known and other as-yet unknown infectious agents from the thawing regions of our world have generated concern among top researchers. Jean-Michel Claverie a professor of microbiology at Aix-Marseilles University recently noted to BBC:

“Following our work and that of others, there is now a non-zero probability that pathogenic microbes could be revived, and infect us. How likely that is is not known, but it’s a possibility. It could be bacteria that are curable with antibiotics, or resistant bacteria, or a virus. If the pathogen hasn’t been in contact with humans for a long time, then our immune system would not be prepared. So yes, that could be dangerous.”

A Context of General Disturbance

Overall, it is likely that there are more numerous climate influences to disease transfer than mere heating and thawing. The general disturbance to the natural world generated by more extreme fires and floods, by instances of flash drought, and even by the mechanism of rising seas is likely to displace more disease reservoirs, creating previously unknown illness transmission potentials.

As far as our general scientific knowledge of illness related to or influenced by the climate crisis at this time, what we see now is likely the tip of the proverbial iceberg. And, as with all things climate crisis related, we require more research, more knowledge-sharing, more general public support of scientific discovery to pull back the veil on this particular new threat. So in conclusion of this chapter on the climate crisis relationship to human illness, we’ll depart with a statement from the World Health Organization:

Changes in infectious disease transmission patterns are a likely major consequence of climate change. We need to learn more about the underlying complex causal  relationships, and apply this information to the prediction of future impacts, using more complete, better validated, integrated, models.

Up Next — Harmful Contacts with our Living Earth and Redounding Shots Across the Bow

Introduction — Climate of Pandemic

Electron microscope image of first COVID-19 case in US. Viral particles are colored blue. Image source: CDC.

Climate change currently contributes to the global burden of disease and premature deaths (very high confidence). — IPCC


One disease.

Just a single nasty bug. COVID-19.

An illness resulting from the virus SARS-CoV-2.

That’s all it took to bring global civilization to a grinding, crashing, train-wreck like halt. Not a collapse. But more of a rational-fear freeze.

And now here we are, 3.38 billion souls at least, sheltering at home or under some form of confinement. Waiting in isolation as medical professionals struggle to keep a growing flood of our fellow human beings — in hospitals or triage tents — alive and breathing. For COVID-19 kills by essentially filling our lungs up with viral glass like nodules and fluid due to the body’s defensive immune response. This is the social climate of our presently distanced public life. A fearful Climate of Pandemic.

How did we get here? How do we get out? And how might the increasingly disturbed Earth system climate have influenced the spread of this particularly nasty illness? Most important of all, how can we make ourselves more aware, more alert, and more resilient to illnesses like COVID-19 in the future?  That is the scope of Climate of Pandemic. An exploration we will undertake here over the coming weeks as this particularly vicious illness ripples across our world.

Why is this important? For one, now more than ever before, we all have a civic and moral duty to listen to and understand the science in all its stripes. Not to deny science. This is not just because we live in a world under siege by the harmful influence of climate crisis. A crisis that, by its very nature, is clastic and fragmental to many structures of our world that we all rely on for life, health, and well-being. One that through various destructive processes multiplies risks to individuals and societies. It is also because we live in what Carl Sagan referred to as A Demon Haunted World. One in which scientific ignorance and superstition — denial — is actively promoted by some leaders as a false alternative to fact and reason.

Science is our candle in the darkness in a rising wind. It can give us a predictive indicator of what may be in store as a result of the climate crisis and its coordinate pandemic crisis. In that understanding, it can provide a guide to make the crisis and its related offspring and out-castings less damaging through various actions. And if we listen to science, we can act to save lives and life support systems — both human and environmental — now.

The climate crisis itself stretches to contain a very broad diversity of threats. Some of these threats it directly causes. Others, as is likely the case with COVID-19, it influences in a number of ways to make them more dangerous or potentially more likely to spread. Cause and influence are both important threat relationships of the climate crisis. But they are also important to distinguish.

This does not mean that influence should be overly diminished. For example, the climate crisis influences the strength of hurricanes. It does not cause a hurricane. But if a hurricane is influenced in such a way that in the present climate it is now a category 5 storm where it would once have been a category 2 storm, then the climate crisis influence is a seriously destructive one.

I suspect that the influence relationship between climate and disease is similarly substantial. Perhaps not with COVID-19 particularly. But maybe so. Or maybe somewhere in between. The nuanced degree a known unknown at this time. But one that the process of scientific discovery will likely unravel more for us as we look closer. In any case, the broader context given by IPCC indicates that the climate crisis already is a major contributor to the global burden of disease.

So it is important to be clear that the climate crisis did not cause COVID-19. The illness existed before, likely in bats and in civets or in pangolins and civets. But it may have provided impetus for the illness to amplify in bats or pangolins and to spread through other species ultimately to humans. And the drivers of the climate crisis such as air pollution from fossil fuel burning or its upshots such as wildfires, extreme heat, and extreme weather may have also amplified the illness’s impact once it did make the leap into humans.

All are subjects we’ll dive into more deeply later in this work.

For now, we are going to take a step back from COVID-19 itself and look more broadly at the scientific understanding of how the climate crisis impacts diseases in general and presents a higher risk of deadly illnesses making their way into the human population. Because when it comes to understanding larger threats, context is often everything.

(Up Next — From Ancient Reservoirs)

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