Science points to causes of COVID-19

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Coronaviruses are transmitted between animals and humans. Many are relatively harmless – causing no more than a common cold. Others result in diseases that are new and unfamiliar, like the COVID-19 pandemic, and before that, outbreaks of diseases like Severe Acute Respiratory Syndrome or SARS (2002); Avian Influenza or bird flu (2004); H1N1 or Swine  Flu (2009); Middle East Respiratory Syndrome or MERS (2012); Ebola (2014– 2015); Zika virus (2015–2016); and West Nile virus (2019).

Almost a century’s worth of global trends confirm that coronaviruses are occurring more frequently. A 2016 UN Environment Programme (UNEP) report flagged coronaviruses–or “zoonoses­­”–as an issue of global concern. On average, three new infectious diseases emerge in humans every year; and about three quarters of these are zoonotic.

What is causing the spike in these diseases?  Here’s what decades of scientific research has to say: 

Coronaviruses are facilitated by human actions

According to the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services, “There is a single species that is responsible for the COVID-19 pandemic – us.”

Not all coronaviruses result in disease. Without animal-to-human transmission, the current SARS-CoV-2 virus would not have presented itself in the form of COVID-19.  Indeed, other coronaviruses are circulating in animals and have not yet infected humans.

Coronaviruses are leaping to humans more frequently because we are providing them with more opportunities to do so. In the last 50 years alone, the human population has doubled and the global economy has almost quadrupled. Rapid migration from rural to urban areas and creation of new urban centres has affected demographics, lifestyles and consumer behaviour. 

Environmental changes

Our evolving lifestyles have dramatically altered the land around us. We have cleared forests and other natural areas to create spaces for urban areas and settlements, agriculture and industries. In doing so, we have reduced overall space for wildlife and degraded natural buffers between humans and animals.

Climate change is also a driver of zoonoses.  Greenhouse gas emissions–primarily the result of burning fossil fuels–cause changes in temperature and humidity, which directly affects the survival of microbes.  Scheduled for release next month, a new rapid assessment by UNEP and ILRI on zoonotics suggests that epidemics will become more frequent as the climate continues to change. 

Behavioural changes

Demand for dairy and meat products has led to the expansion of uniform cropland and intense livestock farming in rural areas and near cities.  Livestock often serve as a bridge between wildlife and human infections, meaning pathogens may be passed from wild animals to livestock to humans. 

Of particular concern are informal markets, where live, wild animals are kept and sold, often in unsanitary and unhygienic conditions. Viruses and other pathogens may be easily spread among animals that are kept close together; or to the humans who handle, transport, sell, purchase or consume them, when sanitary and protective practices are not followed. 

Pathogen changes

Pathogens are always changing to survive in different animals, humans and environments. With the increase of intensive farming and overuse of antimicrobial drugs in both animals and people, pathogens are becoming more resistant to the very medications that might have been effective in treating zoonotic disease.

What COVID-19 is teaching us

COVID-19 is a reminder that human health and the planet’s health are closely linked. There are about 8 million species of life on the Earth, of which humans are just one. These include an estimated 1.7 million unidentified viruses, recognized as the type that may infect people, existing in mammals and water birds.  Any one of these could be transferred to humans, if we don’t take preventative measures now.

The most fundamental way to protect ourselves from coronaviruses is to prevent destruction of nature, which drives the spread of diseases

Where ecosystems are healthy and biodiverse, they are resilient, adaptable and help to regulate diseases. Pathogens that are passed around among reservoirs in animals are more likely to reach dead–and effectively die off–where there is greater diversity.

Genetic diversity builds disease resistance among animal populations and decreases the chances of outbreaks of high-impact animal diseases, according to a 2017 IPBES report.  Conversely, intensive livestock farming can produce genetic similarities within herds and flocks, reducing resilience and making them more susceptible to pathogens. This, by extension, exposes humans to a higher risk.

Behavioural changes

Demand for dairy and meat products has led to the expansion of uniform cropland and intense livestock farming in rural areas and near cities.  Livestock often serve as a bridge between wildlife and human infections, meaning pathogens may be passed from wild animals to livestock to humans. 

Of particular concern are informal markets, where live, wild animals are kept and sold, often in unsanitary and unhygienic conditions. Viruses and other pathogens may be easily spread among animals that are kept close together; or to the humans who handle, transport, sell, purchase or consume them, when sanitary and protective practices are not followed. 

Pathogen changes

Pathogens are always changing to survive in different animals, humans and environments. With the increase of intensive farming and overuse of antimicrobial drugs in both animals and people, pathogens are becoming more resistant to the very medications that might have been effective in treating zoonotic disease.

What COVID-19 is teaching us

COVID-19 is a reminder that human health and the planet’s health are closely linked. There are about 8 million species of life on the Earth, of which humans are just one. These include an estimated 1.7 million unidentified viruses, recognized as the type that may infect people, existing in mammals and water birds.  Any one of these could be transferred to humans, if we don’t take preventative measures now.

The most fundamental way to protect ourselves from coronaviruses is to prevent destruction of nature, which drives the spread of diseases

Where ecosystems are healthy and biodiverse, they are resilient, adaptable and help to regulate diseases. Pathogens that are passed around among reservoirs in animals are more likely to reach dead–and effectively die off–where there is greater diversity.

Genetic diversity builds disease resistance among animal populations and decreases the chances of outbreaks of high-impact animal diseases, according to a 2017 IPBES report.  Conversely, intensive livestock farming can produce genetic similarities within herds and flocks, reducing resilience and making them more susceptible to pathogens. This, by extension, exposes humans to a higher risk.

UN Environment

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