What to know about the history of coronaviruses

Coronaviruses are a large, diverse group of viruses that may cause diseases in humans and other animals. Although experts first identified coronaviruses in the mid-1900s, they have likely existed for thousands of years.

These viruses most commonly affect cats, bats, pigs, and camels. However, some coronaviruses can evolve to cause infections in humans.

Although “coronavirus” often has associations with the SARS-CoV-2 virus that caused the COVID-19 pandemic, many different coronaviruses exist. Many never have the ability to cause infections in humans, and the viruses vary in terms of how contagious and harmful they are.

Read more to learn about how researchers discovered coronaviruses, how they have evolved, and what scientists expect in future coronaviruses.

How old is coronavirus?

Some say researchers first discovered coronaviruses in the mid-1960s. Other sources report identifying coronaviruses as early as 1937Trusted Source.

However, like many viruses, coronaviruses have been circulating in human populations for thousands of years. While it is impossible to know just how old they are, coronaviruses have likely been around far longer than humans have known about them.

Some research has investigated historic coronaviruses.

In a 2021 studyTrusted Source, researchers looked at genomic data from 2,500 modern humans. This data showed that an ancient form of coronavirus existed more than 20,000 years ago in what is now East Asia.

What was the first coronavirus?

Medical students at the University of Chicago discoveredTrusted Source the first coronavirus known to affect humans. Formally called HCoV-229E, experts know it as 229E.

Much like the common cold, 229E is a mild-to-moderateTrusted Source upper respiratory illness. Many people will have it or another similar coronavirus in their lifetime and never know it.

The first coronavirus to cause widespread illness in humans in modern history is SARS-CoV. Likely originating in bat populations, experts first discoveredTrusted Source it in 2002, and it went on to affect over 8,000 people in 29 countries.

However, the SARS outbreak was not widespread enough for health officials to consider it a pandemic. The first coronavirus that received pandemic classification was the SARS-CoV-2 virus that caused the ongoing COVID-19 pandemic.

How coronaviruses have evolved

Of the hundreds of viruses in the coronavirus family, the majority causeTrusted Source mild-to-moderate respiratory illnesses that share similarities to the common cold.

There are seven types of coronavirus known to cause illness in humans:

• 229E (alpha coronavirus)
• NL63 (alpha coronavirus)
• OC43 (beta coronavirus)
• HKU1 (beta coronavirus)
• MERS-CoV
• SARS-CoV
• SARS-CoV-2

In the past two decades, some coronaviruses have evolved in animal species to the point where they can cause infections in humans. This is called a “spillover event.”

The human immune system is not familiar with these viruses, so they tend to cause serious illness and spread easily.

Three species of coronavirus can cause serious and sometimes even fatal infections:

• SARS-CoV
• MERS
• SARS-CoV-2

SARS-CoV

Commonly referred to as SARS, health experts first identified this virus in Southern China in November 2002.

Since 2004, there have been no reported human cases of SARS infections. However, the virus is likelyTrusted Source still in existence to some extent.

During the SARS outbreak, the illness had a 9.6%Trusted Source mortality rate.

MERS-CoV

Researchers identified the next species of coronavirus to cause major disease in Saudi Arabia in September 2012. They called it MERS-CoV (Middle East Respiratory Syndrome coronavirus), or MERS.

Although it is less common now, MERS continues to cause sporadic, localized outbreaks in some parts of the world, primarily the Arabian Peninsula. As of 2019, only two infections affected people living in the United States, both of which occurred in 2014.

The mortality rate associated with MERS infections is 35%Trusted Source. However, this number may be inaccurate because of a lack of case documentation.

SARS-CoV-2

Some researchers think SARS-CoV-2, which causes the disease COVID-19, first evolved to cause human infections in China around December 2019. However, this may simply be the first place where researchers identified the infection from the virus.

On March 11, 2020, the World Health Organization (WHO) declared COVID-19 a global pandemic. This means it was causing widespread global illness.

Although the precise source of SARS-CoV-2 remains unknown, some early experts think it may have started in bats.

While its associated disease COVID-19 has a lower mortality rate than SARS and MERS, SARS-CoV-2 is also more contagious. According to current estimates, the currently circulating coronavirus has undergone around a hundred different mutations so far.

The CDCTrusted Source has identified the Delta and Omicron strains as variants of concern. As of January 2022, the Omicron variant has caused more than 96% of COVID-19 cases in the United States.

Where did SARS-CoV-2 come from?

According to what researchers currently know, SARS-CoV-2 appears to have first caused infections in humans in Wuhan, the capital of the Hubei province in China.

However, the exact source of SARS-CoV-2 remains unknown.

What do scientists expect in future coronaviruses?

From an evolutionary perspective, it is in a virus’s best interest to become less deadly and more contagious. This is what the SARS-CoV-2 variant, Omicron, seems to be doing.

The ultimate goal of a virus is to replicate and circulate as many copies of its RNA, or genes, as possible.

This means that in most cases, the virus does not want to kill or cause severe illness in its host, as doing so limits its ability to reproduce and spread.

In an ideal world for most viruses, they will cause infections that do not interfere with someone’s ability to go out and spread the virus as much as possible, or even better, cause no noticeable symptoms at all.

There are instances in history of viruses evolving to become less dangerous. For example, the H1N1 influenza virus associated with the 1918 “Spanish flu” later became the far less deadly 2009 “swine flu.”

Therefore, when considering how SARS-CoV-2 will evolve, experts thinkTrusted Source it makes evolutionary sense for the virus to become less deadly and more contagious. However, this does not mean it will. Viruses are unpredictable, and it is impossible to know what a new strain of SARS-CoV-2 or new virus will bring.

Summary

Although experts first identified coronaviruses in the mid-1900s, they have likely been circulating in human populations for thousands of years.

Many coronaviruses are relatively harmless and cause mild-to-moderate respiratory symptoms. However, some coronaviruses, such as SARS, MERS, and SARS-CoV-2, have a greater impact on populations.

It is impossible to know how future coronaviruses will affect humans, but they will likely become more contagious and less harmful over time.

Source - Medical News Today

Reverse zoonosis: Can you make your pet sick?

 For good reason, there is a great deal of interest in the transmission of diseases from animals to humans. Recently, however, medical researchers have started to ask the opposite question: can we make animals sick?

Swine and bird flu are two of the most recent and startling examples of animals passing diseases to humans.

Other unpleasant pet-to-human medical problems include ringworm, roundworm, and hookworm, as well as beaver fever, toxoplasmosis, and rabies.

Although these animal-to-human transmissions are relatively well described, pathogenic traffic in the opposite direction is much less well understood.

In this Spotlight feature, we will investigate whether pathogens can travel from humans to animals in a process referred to as reverse zoonosis, or anthroponosis.

A review of current literature on this topic, published in PLOS One in 2014, identified a wealth of examples. They found cases of bacteria, viruses, parasites, and fungi jumping from human hosts to animal-kind to occur across 56 countriesTrusted Source on every continent with the exception of Antarctica.

The importance of reverse zoonoses

Reverse zoonosis is not just an interesting concept; it is an important global issue. Animals bred for food are transported far and wide, interacting with wild species that they would never naturally have encountered. With a rapid growth in animal production and an increase in the movement of both animals and people, a human pathogen within an animal could potentially move thousands of miles in just 24 hours.

For instance, during the H1N1 influenza pandemic of 2009, the virus was able to travel the breadth of the planet and from pigs to humans in a matter of months.

On top of the increasing animal trade, we have an ever-growing pet industry. An estimated 68 percent of people in the United States owned a pet in 2015 and 2016, up from 56 percent in 1988. Humans, animals, and disease are more entwined than ever.

Understanding how diseases work across all scenarios is essential for the future success of the human food chain and our survival as a species.

Although guidelines, protocols, and legislation attempt to keep on top of the increased movement of animals across the planet, the size of the issue is immense. Above and beyond legal farms and markets, zoos and aquariums, there is also an illegal meat trade that has the potential to affect the situation significantly. For instance, some estimateTrusted Source that 5 tons of illegal bushmeat move through Paris’ Roissy-Charles de Gaulle airport every week in personal luggage.

Early research into human to animal pathogens

The fact that diseases can pass from humans to animals is, perhaps, not such a surprise. An estimated 61.6 percentTrusted Source of human pathogens are regarded as multiple species pathogens and are able to infect a range of animals. Also, over 77 percent of pathogens that infect livestock are multiple species pathogens.

Although investigating these interactions is not a new endeavor, interest in the field has grown and developed over recent years. One of the earliest studies demonstrating reverse zoonosis was conducted in 1988 and looked at dermatophytesTrusted Source – fungi that cause superficial infections of the skin, nails, and hair – including Microsporum and Trichophyton. The authors found that these fungi could be transmitted from animal to animal, human to human, animal to human, and human to animal.

In the mid-1990s, focus moved from fungal reverse zoonoses to bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis.

In the late 1990s, interest in viruses picked up, peaking during the 2009 H1N1 swine flu pandemic. From 2000, studies began to emerge investigating the ability of certain parasites to pass from human to animal, including Giardia duodenalis (the parasite responsible of giardiasis) and Cryptosporidium parvum (a microscopic parasite that causes the diarrheal disease cryptosporidiosis).

Below, we outline a selection of pathogens that have been observed jumping the gap between human and animal.

MRSA transferred from humans to their pets

MRSA is sometimes called a “superbug” because of its resilience to antibiotics. Infections caused by MRSA are notoriously difficult to treat and have the potential to be fatal.

Although cases of MRSA in the U.S. appear to be decliningTrusted Source, it is still a significant public health concern.

A study, published in the journal Veterinary Microbiology in 2006, looked at MRSA in pets and its transmission between humans and animals. They concludedTrusted Source that:

“Transmission of MRSA between humans and animals, in both directions, was suspected. MRSA appears to be an emerging veterinary and zoonotic pathogen.”

The paper mentions a specific case in which a couple was repeatedly infected with MRSA. The re-infections only stopped once their dog was identified as the source and treated. It is presumed that the dog was initially infected by the couple and then passed the infection back to them each time they had been successfully treated.

With the inherent difficulties of treating MRSA, it is a genuine concern if animals – and particularly pets – are able to contract and transmit the pathogen. As the authors write: “The emergence of MRSA in household pets is of concern in terms of animal health, and perhaps more importantly, the potential for animals to act as sources of infection or colonization of human contacts.”

Tuberculosis in a Yorkshire terrier

A paper, published in 2004, describes the case of a 3-year-old Yorkshire terrier who arrived at the University of Tennessee College of Veterinary Medicine with anorexia, vomiting, and a persistent cough.

After running a barrage of tests – including, sadly, an eventual postmortem – the authors concluded that it had contracted tuberculosis (TB) (Mycobacterium tuberculosis). The dog’s owner had been receiving treatment for TB for 6 months. This was the first documented transmission of TB from human to canine.

Cats are also susceptible to TB, but they most commonly catch cattle TB (M. bovis) or, more rarely, a version of the disease carried by birds (M. avium).

Dogs are not the only animals that can be affected by humanborne TB. There have been a number of documented cases of elephants contracting TB from humans, including threeTrusted Source from an exotic animal farm in Illinois.

Cats catching flu from humans

In 2009, the first recorded case of fatal human-to-cat transmission of the H1N1 flu virus occurred in Oregon. The owner of the cat had a severe case of influenza and had to be taken to the hospital. Her cat – an indoor cat with no exposure to other people or animals – later died of pneumonia caused by an H1N1 infection. Details of the case were published in the journal Veterinary PathologyTrusted Source.

In 2011 and 2012, researchers identified more than 13 cats and one dog with pandemic H1N1 infection that appeared to have come from human contact. Interestingly, the animals’ symptoms were similar to those experienced by human carriers – rapidly developing respiratory disease, a lack of appetite and, in some cases, death.

Fatal respiratory illnesses in chimpanzees

Of all the animals, gorillas and chimpanzees are perhaps most susceptible to human ailments, thanks to their similar genetic and physiological makeup. They are known to be vulnerable to a number of human diseases, including measles, pneumonia, influenza, a range of viruses, bacteria, and parasites.

Due to poaching, habitat loss, wildlife parks, zoos, and bushmeat hunting, humans more frequently come into close proximity with primates. Because of this, cross-species transmission of diseases is becoming a pressing concern.

In 2003, 2005, and 2006, outbreaks of fatal respiratory disease struck the wild chimpanzees at the Mahale Mountains National Park in Tanzania. Although measles and influenza were both considered, no evidence to support them as the cause could be found.

Researchers analyzed stool samples from affected and nonaffected individuals, and they identified that a human-related metapneumovirus – a virus that causes an upper respiratory infection – was to blame.

This dwindling population of chimpanzees was being decimated by a cold transferred to them by humans.

Similarly, in 2009, an outbreak of human metapneumovirus infection in Chicago, IL, spread from infected zookeepers to a group of captive chimpanzees. All seven became ill, and one died as a resultTrusted Source.

African painted dogs

African painted dogs are an endangered species of wild dog. As part of the conservation effort, a studyTrusted Source published in 2010 investigated the parasites present in the species’ feces.

Infection by Giardia duodenalis, a parasite that lives in the small intestine, was found in 26 percent of wild animals and 62 percent of captive animals.

Although common in domestic cats and dogs, G. duodenalis is not a parasite naturally found in African painted dogs. Additionally, the strains of parasite found in the dogs’ feces were of a subtype commonly associated with humans, rather than the subtypes usually seen in pet dogs.

Symptoms of the disease can include diarrhea, nausea, abdominal discomfort, and reduced appetite.

The authors concluded that the parasites had entered the population from human-dog interactions and, from then on, were passed from dog to dog, becoming a new potential threat to their already uncertain future.

Although research into reverse zoonosis is relatively scant, it is an important and urgent field of study. If human pathogens are able to infect other species, and these species are able to interact with humans and travel great distances, it is a pandemic waiting in the wings.

We already know that the flu virus can mutate quickly, and by living in different species, it has the chance to change and mutate in ways that it could not in humans. As these pathogens change, they might become less dangerous to humans. On the other side of the coin, however, some might become increasingly deadly.

Source - Medical News Today

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How COVID-19 has changed the face of the natural world

 All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub and follow our live updates page for the most recent information on the COVID-19 pandemic.

On the human front, most pandemic-related news has been negative.

So far, COVID-19 has caused the deaths of more than 3 million people worldwide, and that number could be significantly higher given how challenging it is to track every COVID-19 death.

A viewpoint article in JAMATrusted Source estimates that the COVID-19 pandemic may cost the United States at least $16 trillion, roughly 90% of the total annual U.S. gross domestic product (GDP).

Despite this, on paper, it would make sense to assume that the natural world, at least, is getting a bit of a break. A world in which humans are traveling far less should offer major environmental benefits.

But are wildlife and the climate really benefitting from the pandemic? In this Special Feature, Medical News Today explores what is currently known about the potential impact of the COVID-19 pandemic on wildlife and the climate

Wildlife and COVID-19: The good

One major and predominately positive benefit of the pandemic for wildlife is less human travel.

Due to the significant reduction in journeys, fewer people are hitting and injuring or killing wildlife on roadways.

A study from March 2021 found that hedgehog roadkill rates in Poland were more than 50% lower compared with pre-pandemic years, saving tens of thousands of hedgehogs in Poland alone. This may help reverse the long-term decline of European hedgehog populations.

Another study analyzing roadkill data from 11 countries found that roadkill rates fell by more than 40% during the first few weeks of the pandemic restrictions in Spain, Israel, Estonia, and the Czech Republic.

In addition, fewer ships are traveling through the world’s waterways and oceans for shipping, fishing, aquaculture, and tourism purposes.

In November 2020, experts predicted that global maritime trade would have plunged by 4.1% by the end of that year. Other reports estimated a 10% decline in the container trade for 2020.

A reduction in water travel and activity could reduce the risk of ships striking and injuring or killing marine animals. It may also reduce the marine disruption that occurs due to noise pollution from ships, fishing sonar, and recreational boats.

Birds might also be benefitting from the sharp decline in air travel, which may have vastly reduced the risk of bird strikes.

According to the Federal Aviation Administration, between 1990 and 2019, there were about 227,005 wildlife strikes with civil aircraft in the U.S. In addition, U.S. airplanes reported some 4,275 more wildlife strikes at foreign airports. These strikes resulted in injury to 327 people.

The pandemic has also led to a declineTrusted Source in industry supply chains, reducing demand for commercial activities that exploit natural resources in many parts of the world. For example, lower fishing demand and activity may reduce the removal of animals from the wild.

And in India, anecdotal reports suggestTrusted Source that reduced fishing and vehicle traffic at nesting beaches may be boosting populations of the critically endangered olive ridley sea turtle.

The pandemic may even benefitTrusted Source wildlife by disrupting the hidden, generally illegal supply chains that destroy wild populations, including those that fuel the wildlife trade.

Going forward, authorities may start to take more immediate, forceful action against the illegal exploitation and transportation of wild animals globally. The World Health Organization (WHO) released a reportTrusted Source at the end of March suggesting that although the precise origin of the pandemic remains elusive, the global wildlife trade could have allowed the virus to enter China.

“This report highlights the urgent need to curb wildlife exploitation and signals that wildlife trade could have led to the pandemic,” says Tanya Sanerib, the international legal director at the Center for Biological Diversity.

“Disease risk is a global threat. Whether a bat is captured for food in Southeast Asia or to make a paperweight for a desk in the U.S., people’s demand for wildlife anywhere in the world creates a risk of new diseases emerging.”

– Tanya Sanerib

People are also reporting seeingTrusted Source wildlife in unexpected places, such as in large cities and commercial harbors. The increased number of animals in urban environments is likely due to reductions in human presence, air and water pollution levels, and noise pollution.

For example, people have spotted pumas wandering in downtown Santiago, Chile, and dolphins swimming in the usually choppy waters of the Port of Trieste, Italy.

Wildlife and COVID-19: The bad

However, many of the immediate positive effects of the pandemic on wildlife — such as reduced road, air, and ship deaths or disruption — will likely reverse if the world goes back to business as usual.

And in many cases, it will take generations of change to help thousands of species around the world recover from the impact of humankind. For example, it may take 10–15 years of sustained reduced fishing to allow the world’s depleted fish populations to recover.

Some studies have also found that the pandemic may actually be causing harm to wildlife.

In one studyTrusted Source, researchers found that reduced human disturbance relating to lockdown has benefitted invasive alien species by interrupting the actions that people were taking to control them. The authors also claim that pandemic restrictions have reduced the work of conservation and law enforcement organizations that care for wildlife and protected areas.

And this is a global trend, as the staff of preserves, game parks, sanctuaries, and other wildlife facilities are unable to perform their normal activities.

Also, the reduction in law enforcement may cause a sudden increase in illegal wildlife killing — in particular, that of endangered animals liable to persecution or poaching.

Some experts also worry that economic hardship in low income countries may lead to an increase in natural resource exploitation, such as unlicensed logging and the illegal wildlife market, as people run out of ways to earn a living.

According to satellite images, a surgeTrusted Source in deforestation is taking place in several hotspots. Also, illegal fishing rates are on the rise in Brazil and the Philippines.

The changes in human activity that the pandemic has necessitated may also be having some negative effects. For instance, some species that rely heavily on humans for feeding or scavenging, such as monkeys, gulls, and rats, may be strugglingTrusted Source during the pandemic.

People may also be using outdoor spaces such as parks and nature reserves more during lockdown, which could disturb resident wildlife unaccustomed to human interactions.

On the flip side, reduced ecotourism rates are crippling many organizations worldwide that rely on human visitors to feed and care for their animals.

Meanwhile, plastic pollution from improperly disposed-of single-use COVID-19 protective gear also seems to be increasing the global plastic pollution problem and causing wildlife deaths, as animals can ingest plastic items or become entangled or trapped in them.

According to one estimate, people are throwing away as many as 3.4 billionTrusted Source single-use face masks and face shields daily worldwide.

COVID-19 and air and water pollution

Many studies from all over the world have reported that the pandemic has brought about significant reductions in climate and water pollution.

One study found that daily global CO2 levels dropped by 17%Trusted Source during the early months of the pandemic. Similarly, other research showed that levels of the pollutant nitric dioxide lowered drastically, by 20–40%, across the U.S., Western Europe, and China.

An analysis of dataTrusted Source from 44 Chinese cities also found that pandemic travel restrictions resulted in reductions of between 4.58% and 24.67% in five major air pollutants.

An American studyTrusted Source suggests the reason for this, finding that between March 27 and May 14, 2020, in one Massachusetts neighborhood, car travel reduced by 71%, and truck traffic fell by 46%.

These reductions reduced levels of the harmful particles present in vehicular emission, decreasing black carbon by 22–46% and ultrafine particle number concentration by 60–68%.

A studyTrusted Source from Brazil also found that during the partial lockdown in São Paulo, levels of nitric oxide decreased by up to 77.3% while carbon monoxide dropped by up to 64.8% compared with 5-year monthly averages.

In another studyTrusted Source from September 2020, researchers claim that the pandemic situation has been improving air quality, reducing greenhouse gas emissions. It also seems to have reduced the pressure on sensitive tourist destinations, such asTrusted Source heavily visited beaches.

Experts suggest that the unprecedented decrease in air pollutant emissions during the pandemic could reduce seasonal ozone concentrations.

They estimate that global and European emissions may fall by 30–50% for the industry, energy, international shipping, and road transport sectors, and by 80% for the aviation sector.

Travel restrictions and reduced commercial activity may also be improving the health of the world’s bodies of water.

One study found that pollution levels dropped by nearly 16% in India’s longest freshwater lake during a lockdown period. Another studyTrusted Source found that COVID-19-related beach closures and travel restrictions reduced the amount of trash leaking into the marine environment off the coast of Kenya.

Improvements in air quality often translate into water quality improvements given how closely the ocean and atmosphere are related.

A pandemic of change?

Many researchers and wildlife organizations are urging scientistsTrusted Source and other stakeholders globally to use this unprecedented time for a close examination of the impact of human activity on the natural world.

They argue that the information that researchers gather during this time could help improve conservation and biodiversity efforts.

It may also improve their ability to predict global environmental changes and potential cases of zoonoses, the transmission of disease from animals to humans. This could save millions of human lives, and economic losses, going forward.

Realistically, it will take years to assess exactly how the COVID-19 pandemic has affected wildlife, the environment, and the climate.

Moreover, the impact of the pandemic on the natural world is unlikely to be linear. ResearchTrusted Source suggests that a reduction in some pollutants, including nitrogen oxides, may result in the rise of others, such as ozone.

Understanding how this pandemic has changed humans’ relationship with nature may be just as complex.

But for now, these positive changes may be enough to give some people, and Mother Nature, the hope of a better future.

It may also help illuminate flaws in how humans interact with and value nature, which could have long lasting, permanent repercussions for humans and the environment alike.

Source -Medical News Today