There are nearly a million viruses out there waiting to make the jump from animals to humans, experts say.
And according to a new report, by treating the environment badly, we're making it more likely they will.
"Diseases that we get like COVID come from wildlife - and so the more that we encroach and go into habitats where wildlife are, the more complex they are and the more likely that these emergent events will happen," David Hayman of Massey University's School of Veterinary Science told Newshub.
"This is true for COVID, HIV/AIDS, Ebola - all a similar process."
Since making the leap to humans last year, the SARS-CoV-2 virus - which causes a range of symptoms, together known as COVID-19 - has killed at least 1.2 million people. It's believed to have originated in bats, before making the leap to humans - possibly via another animal, such as the pangolin.
A new report from the United Nations' Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), compiled by 22 experts, says it's "no great mystery" what caused this pandemic - or any before it.
"The same human activities that drive climate change and biodiversity loss also drive pandemic risk through their impacts on our environment," said IPBES chair and zoologist Peter Daszal.
"Changes in the way we use land; the expansion and intensification of agriculture; and unsustainable trade, production and consumption disrupt nature and increase contact between wildlife, livestock, pathogens and people. This is the path to pandemics."
The report makes a number of recommendations, including:
- stopping the trade in animals known to be carriers of zoonotic diseases (able to infect both humans and animals)
- introducing taxes and levies on meat consumption to discourage habitat destruction and expansion of agriculture, and other activities that increase the risk of pandemics
- setting up an international pandemic prevention council.
"There are high-risk activities like wildlife hunting - there are things that we do that increase the likelihood," said Dr Hayman.
"Deforestation, things like palm oil - the way that we buy things in the West can have implications a long way away. I think it's really both individually but also collectively as nations thinking about what we can do to mitigate [the risk].
"And also include the cost of these things in what we do - people don't often count these costs when they're felling a tree. They just value the tree. But what are the costs involved? ... We need to maybe pay more for some things to prevent long-term costs being incurred."
The report estimates there are another 1.7 million viruses yet to be discovered in nature, around half of which "could have the ability to infect people".
Dr Daszak says it's not a matter of figuring out how to avoid another pandemic - but leaders having the will to implement the necessary changes.
"We have the increasing ability to prevent pandemics - but the way we are tackling them right now largely ignores that ability. Our approach has effectively stagnated - we still rely on attempts to contain and control diseases after they emerge, through vaccines and therapeutics.
"We can escape the era of pandemics, but this requires a much greater focus on prevention in addition to reaction."
By July next year, the report estimates COVID-19 would have cost the global economy perhaps as much as US$16 trillion (NZ$24 trillion) - 100 times more than what it would have cost to prevent it.
"The IPBES report is absolutely right in showing why prevention is so much better than cure, and that the cost of prevention is considerably less than those of the impacts," said Mike Rivington, climate and environment scientist at the UK's James Hutton Institute.
"Whilst there may be a cure for COVID-19 in the future, there is not a cure for climate change and biodiversity loss if these pass critical tipping points. Preventing climate change and biodiversity loss and altering the focus of our food systems from efficiency to resilience will substantially reduce future risks from pandemics and ecosystem degradation."
John Spicer, professor of Marine Zoology at the University of Plymouth, said the report shows treating the environment well will solve numerous "interconnected, inextricable, inescapable" issues.
"This report highlights that our COVID-19 crisis is not just another crisis alongside others - the biodiversity crisis and the climate change crisis.
"Make no mistake, this is one big crisis - the greatest that humans have ever faced. And it's not going to be averted by talk, tinkering or pretending it's 'fake news' - this latest IPBES Workshop on Biodiversity and Pandemics report makes that crystal clear."