By Professor Tim Benton
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The world is grappling with the novel coronavirus, which has spread from China to at least 16 other countries, including the United Kingdom.
Outbreaks of new infectious diseases are generally considered "unique".
But the new virus, believed to have originated in wildlife, highlights our risk of animal-borne diseases. This is likely to be a bigger problem in the future, as climate change and globalization alter how animals and humans interact.
How can animals make people sick?
In the last 50 years, a number of infectious diseases have spread rapidly after making the evolutionary leap from animals to humans.
The HIV/AIDS crisis of the 1980s originated in great apes, the avian flu pandemic of 2004-07 came from birds, and pigs gave us the swine flu pandemic in 2009. More recently, severe acute respiratory syndrome (SARS) was found to have come from bats, via civets, while bats also gave us Ebola.
Humans have always contracted diseases from animals. In fact, most new infectious diseases originate in wildlife.
But environmental change is accelerating this process, while increased city living and international travel mean that when these diseases emerge, they can spread more rapidly.
How can diseases jump species?
Most animals carry a variety of pathogens: bacteria and viruses that can cause disease.
The evolutionary survival of the pathogen depends on the infection of new hosts, and jumping to other species is one way to do this.
The immune systems of the new host try to eliminate the pathogens, which means the two are locked in an eternal evolutionary game of trying to find new ways to outwit each other.
For example, approximately 10% of infected people died during the 2003 Sars epidemic, compared to less than 0.1% in a "typical" flu epidemic.
Environmental and climate change are eliminating and altering animal habitats, changing how they live, where they live, and who eats whom.
The way humans live has also changed: 55% of the world's population now lives in cities, compared to 35% 50 years ago.
And these larger cities provide new homes for wildlife: rats, mice, raccoons, squirrels, foxes, birds, jackals, monkeys, which can live in green spaces like parks and gardens, away from the waste that humans leave behind.
Wildlife species often thrive in cities rather than in the wild due to the abundant food supply, making urban spaces a breeding ground for evolving diseases.
Who is most at risk?
New diseases, in a new host, are often more dangerous, so any emerging disease is worrying.
Some groups are more vulnerable to contracting these diseases than others.
People living in poorer cities are more likely to work in cleaning and sanitation, which increases their chances of encountering sources and carriers of disease.
They may also have weaker immune systems due to poor nutrition and exposure to poor air or unsanitary conditions. And if they get sick, they may not be able to afford medical care.
New infections can also spread rapidly in large cities, as people are so tightly packed together that they breathe the same air and touch the same surfaces.
In some cultures, people also use urban wildlife for food: they eat animals captured within the city or meat from wild animals harvested in the surrounding areas.
How do illnesses change our behavior?
To date, nearly 8,000 cases of the new coronavirus have been confirmed, and 170 people are believed to have died.
With countries taking steps to stop this outbreak, the potential economic consequences are clear.
Travel bans are now in place, and even without them, people are afraid to interact in case they contract the virus and their behavior changes. Crossing borders is becoming more difficult, seasonal migrant workers are unable to relocate, and supply chains are disrupted.
This is typical of an outbreak of this nature. In 2003, the SARS epidemic cost the global economy an estimated $40 billion (£30.5 billion) over six months. This was partly due to the cost of treating people, but also to economic activity and the movement of people.
What can we do?
Societies and governments tend to treat each new infectious disease as a standalone crisis, rather than recognizing that they are a symptom of how the world is changing.
The more we change the environment, the more likely we are to disrupt ecosystems and create opportunities for disease to emerge.
Only about 10% of the world's pathogens have been documented, so more resources are needed to identify the rest, and which animals carry them.
For example, how many rats are there in London and what diseases do they transmit?
Many city dwellers value urban wildlife, but we must also recognize that some animals pose potential harm.
It makes sense to keep track of which animals are coming into cities and whether people are killing or eating wildlife or taking it to nearby markets.
Improving sanitation, waste disposal, and pest control are ways to help stop these outbreaks from occurring and spreading. More broadly, it's about changing how we manage our environments and how people interact with them.
Pandemics are part of our future
Recognizing that new diseases are emerging and spreading in this way puts us in a stronger position to combat new pandemics, which are an inevitable part of our future.
A century ago, the Spanish flu pandemic infected approximately 500 million people and killed between 50 and 100 million people worldwide.
Scientific progress and large investments in global health mean that this disease will be better managed in the future.
However, the risk remains real and potentially catastrophic: if something similar were to happen again, it would change the shape of the world.
In the middle of the last century, some in the West claimed that infectious diseases were conquerable.
But as urbanization and inequality grow and climate change further disrupts our ecosystems, we must recognize emerging diseases as a growing risk.
Professor Tim Benton is the research director of the Emerging Risks team at Chatham House, where he heads the Energy, Environment and Resources program.
From: https://www.bbc.com/news/health-51237225