How urbanization and the way we deal with animals may influence the spread of illnesses like coronavirus
Pathogens are less likely to ‘die out’ when humans and animals cluster in large groups, says epidemiologist
While health investigators try to pinpoint the exact origin of China's coronavirus outbreak, a prominent public health expert is raising the possibility that urbanization and human-animal interactions are potential contributors to the spread of both the novel coronavirus and other diseases.
Dr. Gregory Gray, an infectious disease epidemiologist and professor at Duke University, said it's too early to lay the blame on any particular animal or human factor for the current outbreak, but several economic conditions may have played a role.
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And if economic patterns did not influence the present situation, they are likely to in future scenarios.
"There are some factors that might support the acceleration of these viruses. Those factors include dense populations of humans and animals that harbour them," said Dr. Gray, who leads an international pathogen research network in 30 countries, including China.
"So there's a continual churning, if you will, of reproduction of viruses as it moves from one host to another," he told CBC Radio's Cost of Living.
So far, the virus seems most closely related to coronaviruses from bats. Many of the patients in Wuhan had a link to a large seafood and live animal market. That origin suggests spread from an animal to a human, according to the U.S. Centers for Disease Control and Prevention.
More people, more animals, more interactions
Over the past century, global populations have concentrated more and more in large cities. This has boosted economic growth and the productivity of nations.
On that front, few countries can rival China in recent decades. The rise of mega-cities combined with population movement has increased the risk of human-to-human infection.
The way forward is to realize that human health, animal health, environmental health and agricultural businesses are all interlinked.- Dr. Gregory Gray, infectious disease epidemiologist, Duke University
The explosive growth in wealth in China has also created a sharp rising demand for meat protein. So by necessity, people have to interact with animals — or meat — more frequently.
That could be through traditional live animal markets, such as the one where the current outbreak has been suspected to originate, or through a more industrialized food chain.
Dr. Gray spoke with Cost of Living host Paul Haavardsrud about these economic factors and what they could mean for current and future disease outbreaks in China and beyond.
Here is part of their conversation..
In what sort of circumstances are we seeing that churning of diseases and in what ways might that be accelerated?
Since we've had the recognition that viruses can move sometimes from wildlife, be amplified in domestic animals, and then periodically infect man, there's been a large emphasis on studying these in various animal species.
We've also, over time, improved our surveillance for pathogens that cause illness in domestic animals.
So these two combined effects have given us a warning that there are quite a few coronaviruses out there in wildlife, and that sometimes new coronaviruses emerge in a number of different swine origins that have caused a huge morbidity and mortality in pig populations.
Was the Asian swine fever we saw last year a coronavirus?
No, that was not a coronavirus, but it's a very good example of how the various farms are connected. If the biosecurity in one farm fails, usually through human behaviour or some other step in the process, a virus can find a way to move to a new farm and you basically see amplification in the new farm.
We are very clearly aware that the biosecurity in these industrialized farming settings and sometimes the small and medium farms need to be improved.
Biosecurity refers to preventative measures designed to protect humans or animals against diseases.
Examples include installing disinfection stations, registering visitors, and parking transport vehicles a mandatory distance from animals.
So is it fair to think about it this way: as the world population grows, and we get more industrialized farming, that's a piece that's contributing to the emergence of all these types of viruses?
I think that's an astute observation and a number of us in the epidemiological field embrace that.
As the world population grows, we are growing more and more dependent on industrialized farming because they can produce protein at a lower cost than ever before.
For very severe diseases for which the clinical recognition is apparent, they're very good at protecting the flocks and herds of animals. But these farms can serve as a hotspot for massive viral or bacterial reproduction, should a virus or bacteria evade the biosecurity and enter.
At the same time, we just can't feed our population without modern agriculture. It's hugely important for food security so we absolutely need large farming. We somehow have to work together to solve these complex problems.
Food security refers to the availability of food and our ability as individuals to access food.
Price, location, scarcity and quality are all potential barriers.
Over the last couple of weeks, was that where your mind started to go to — issues around food security?
Right now there's a lot of focus on the origins of this virus, and most people are thinking about a specific point in time and a specific food market in Wuhan, but there's other data to suggest this virus might have been circulating apart from the animals in the general population.
But yeah, we are aware of all the new coronaviruses that have emerged in the last 10 years in pigs, so it's biologically plausible that novel coronaviruses could come out of a large domesticated animal reservoir and somehow gotten into that market.
[It could be] a mutation of the virus or recombination [and] exchange of genetic material, and a new coronavirus emerged and was suddenly infecting a lot of people.
So there's a lot to be discovered yet. Right now I think it's highly speculative to suggest this was amplified in domestic farms in China.
So what do we do about this? Are there policy steps being brought into new light?
The way forward is to realize that human health, animal health, environmental health and agricultural businesses are all interlinked. We all need each other, we all impact each other.
In a similar fashion, the impact of agricultural businesses on the environment is frequently being attacked by people who are worried about wildlife.
This unwillingness for us to work together has caused some really complex problems. So we need to find new ways to approach this, and one way to approach it is something called "One Health," where you focus on one specific area and you bring everyone to the table and try to work together to study the complex problem, to develop interventions to reduce the problem, and to do so without threatening individual disciplines.
Q&A has been edited for length and clarity.
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