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Viruses and the sick system that destroys our environment

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Pandemics and viral outbreaks aren’t an accident of nature. Fresh research confirms how tearing up animals’ natural habitats and intensive farming are to blame, writes Sadie Robinson
Issue 2700
Deforestation helps to fuel viruses spilling over from animals to humans
Deforestation helps to fuel viruses spilling over from animals to humans (Pic: Wikimedia/Creative Commons)

Systematic tearing up of the environment over centuries has increased the risk of pandemics, according to a new report. 

And as climate change wreaks more havoc, the situation will get worse.

Researchers found that processes such as urbanisation and deforestation have increased the risk of viruses “spilling over” from animals to humans. 

The same processes are putting species at risk of extinction.

Lead author of the report Christine Johnson said, “Spillover of viruses from animals is a direct result of our actions involving wildlife and the habitat. This puts us at risk of pandemics.”

Some have pushed racist, simplistic and short-term explanations for the recent Covid-19 outbreak, such as blaming Chinese people for “eating bats”. 

Yet the report said a “historical account of how humans have altered their contact with animals” over centuries was needed to understand the increase in risk.

Researchers looked at scientific papers on the 142 known viruses that pass from animals to humans. 

They also looked at the risks of extinction for those species, and the causes of their declines.

The evidence suggested that the transmission risk has been highest from species that “have increased in abundance by adapting to ­human-dominated landscapes”.

Domesticated animals, primates and bats had more zoonotic viruses—those that can pass from animals to humans—than other species.

But species threatened due to exploitation or habitat changes had over twice as many zoonotic viruses compared to species endangered for other reasons.


“Our findings provide further evidence that exploitation, as well as activities that have caused losses in habitat quality, have facilitated zoonotic disease transmission,” researchers said.

Drive for profit benefits the spread of disease
Drive for profit benefits the spread of disease
  Read More

The rising number of endangered species due to environmental damage has led to human actions to try and cut the risk of extinction. But this has also put such species in greater ­contact with people.

A group of scientists made similar warnings last month, saying it is almost always human behaviour that causes diseases to spill over. 

Human action doesn’t always lead to species decline. Some thrive and adapt to the changes humans have brought about, such as some bats and rodents.

But the report found that such animals have then shared more viruses with people.

Researchers found that both animal species that are abundant and those in decline can pass diseases to humans. But this isn’t simply a natural process. 

Crucially, it is human exploitation of wildlife habitats and damage to the environment that creates greater risk.

The report concluded that infectious diseases from animals “have emerged at an increased pace within the last century”. 

They “are likely to continue to emerge” as “environmental change is likely to intensify close proximity animal-human interactions in the near future”.

Capitalism is a virus hotspot

The increasing risk of pandemics is to do with how society is organised. Under capitalism profit comes before the safety, health and wellbeing of ordinary people and animals.

Capitalism has drawn millions into huge cities, destroying habitats and drawing more animals into urban areas.

In an agricultural system based on maximising profit, animals are often kept in overcrowded and dirty conditions. 

Big business dominates and farms have grown in size—bringing animals together in bigger numbers. 

And the short-term goal of making money comes before protecting the environment and land for the future.

A system driven by profit will always sacrifice our health and safety. But those at the top prefer to blame “backward” practices in poorer countries.

A recent article in Monthly Review magazine noted that “the capital interests backing production-induced changes in land use and disease emergency” in the Global South blame “outbreaks on indigenous populations”.

They support research that focuses on the outbreak zone of a virus. But looking at the capital interests driving the environmental changes instead suddenly turns New York, London and Hong Kong into “three of the world’s worst hotspots”.

Kept animals share highest number of virues with people

Spillover occurs when a pathogen—an infectious agent such as a virus—is passed from one species to another. 

Zoonoses are infectious diseases that can move from animals to humans. Modern examples include Ebola.

More than two thirds of human viruses are zoonotic. 

But most spillover events don’t lead to the virus then being passed from human to human—for instance rabies.

The report found that wild animals “are the source of the majority of recently emerging infectious diseases”. 

But domesticated animals, including livestock, have shared the highest number of viruses with humans.

The study said there are eight times more zoonotic viruses in domesticated mammalian species compared to wild mammalian species. 

They argue that this is likely to be a result of humans’ close interactions with these animals over centuries.

Domesticated livestock also plays a big role in transmission of zoonotic viruses to humans. 


Researchers found that domesticated species of animals had an average of 19.3 such viruses compared to wild species which had an average of 0.23.

They identified the mammalian species with the highest number of zoonotic viruses shared with humans. 

Those with the highest number of viruses are pigs, cattle and horses with 31 each. 

Sheep had 30, dogs had 27, goats 22, cats 16 and camels 15.

The only wild animals among the top ten were the house mouse with 16 and the black rat with 14.

At the time of the report, more than a fifth of mammalian species were under threat of extinction. 

Exploitation and declines in habitat were partly to blame in over half of the species. 

Both factors are linked to a rising risk of viruses passing from animals to humans.

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