Covid-19 like outbreaks may become common with 'steady stream' of diseases from animals to humans, warns UN

Experts say the rising trend in zoonotic diseases is driven by degradation of the natural environment through land degradation, wildlife exploitation and other stresses


                            Covid-19 like outbreaks may become common with 'steady stream' of diseases from animals to humans, warns UN
(Getty Images)

Ebola, SARS, Zika, West Nile fever and now Covid-19. These are some of the high-profile diseases to emerge in the last several decades. And while they emerged in different parts of the world, they have one thing in common. They are what scientists call "zoonotic diseases", infections that jump between animals and humans, some of which leave illness and death in their wake. Researchers now warn global outbreaks like Covid-19 will become more common — the frequency of infectious diseases jumping from other animals to people is increasing and it will continue to do so due to unsustainable human activities. 

The United Nations (UN) report says that a "steady stream" of animal-borne infectious diseases in the future will be unavoidable unless governments take active measures to prevent zoonotic diseases from crossing into the human population.

"The science is clear that if we keep exploiting wildlife and destroying our ecosystems, then we can expect to see a steady stream of these diseases jumping from animals to humans in the years ahead. Pandemics are devastating to our lives and our economies, and as we have seen over the past months, it is the poorest and the most vulnerable who suffer the most. To prevent future outbreaks, we must become much more deliberate about protecting our natural environment," says Inger Andersen, executive director, United Nations Environment Programme (UNEP), in the analysis.

About 60% of human infections are estimated to have an animal origin and of all new and emerging human infectious diseases, some 75% “jump species” from (non-human) animals to people. While scientists are yet to determine the source of Covid-19, some believe it was passed from bats to a mystery animal species that then passed it on to humans. And while emerging contagions like Covid-19 dominate headlines, neglected zoonotic diseases kill at least 2M people every year in low-income and middle-income countries. That is more than four times the current reported death toll of the coronavirus pandemic, according to the UN. These are often communities with complex development problems, high dependence on livestock and proximity to wildlife.

The report, which is a joint effort by the UNEP and International Livestock Research Institute (ILRI), warns that the rising trend in zoonotic diseases is driven by the degradation of the natural environment. Experts have identified seven human-mediated factors that are most likely driving the emergence of zoonotic diseases: increasing human demand for animal protein, unsustainable agricultural intensification, increased use and exploitation of wildlife, unsustainable use of natural resources accelerated by urbanization, land-use change and extractive industries, increased travel and transportation, changes in the food supply and climate change.

Global hotspot map of estimated risk in zoonotic disease emergence (UNEP/ILRI report)

Many of these seven drivers have shared underlying causes. For example, the growing demand for food can cause agricultural systems to intensify and pay insufficient attention to important consequences related to environmental and human health, changes to food value chains and increased utilization of wildlife, says the research team.

"Covid-19 is one of the worst zoonotic diseases, but it is not the first. Ebola, SARS, MERS, HIV, Lyme disease, Rift Valley fever and Lassa fever preceded it. In the last century, we have seen at least six major outbreaks of novel coronaviruses. Growth in humanity and its activity is largely to blame," says Andersen. She explains, "Meat production has increased by 260% in 50 years. We have intensified agriculture, expanded infrastructure, and extracted resources at the expense of our wild spaces. Dams, irrigation, and factory farms are linked to 25% of infectious diseases in humans. Travel, transport, and food supply chains have erased borders and distances. Climate change has contributed to the spread of pathogens. The end result is that people and animals, with the diseases they carry, are closer than ever.”

According to the researchers, a major constraint to moving towards a pandemic-free world is that most efforts to control infectious diseases are still reactive rather than proactive. During any disease crisis, much effort is spent on developing immediate responses. However, much less investment is made in building communities' resilience to future outbreaks and, even more importantly, in addressing the underlying structural problems or drivers that are causing the recurrence of animal and human epidemics and pandemics.

"To date, most efforts to control zoonotic diseases have been reactive rather than proactive. Covid-19 has made us all aware that it’s time to change that. To prevent future outbreaks of novel zoonotic diseases, we need to address the root causes of their emergence. We need among other things to break down disciplinary and organizational silos, to invest in public health programs, to farm sustainably, to end the overexploitation of wildlife, to restore land and ecosystem health, and to reduce climate change," says Jimmy Smith, Director-General, ILRI.

Meat production has increased by 260% in 50 years and travel, transport and food supply chains have erased borders and distances and as a result, people and diseased animals are closer than ever (Getty Images)

The cost of zoonotic epidemics is steep. The greatest burden of zoonotic disease is borne by poor people, but emerging infectious diseases impact everyone, with monetary losses of emerging infectious disease much greater in high-income countries. The International Monetary Fund has predicted that Covid-19 alone will cause the global economy to contract by 3% this year, wiping out $9 trillion in productivity through 2021. But even in the two decades before the coronavirus pandemic, the World Bank estimated that zoonotic diseases had direct costs of more than $100 billion. The authors write that given that a single zoonotic outbreak can incur trillions of US dollars in costs across the globe, prevention is significantly more cost-effective than response.

The research team has recommended a “one health approach as the optimal method” for preventing as well as responding to zoonotic disease outbreaks and pandemics. "Adopting a one health approach, which unites medical, veterinary and environmental expertise, will help governments, businesses, and civil society achieve enduring health for people, animals and environments alike," they say.

The experts have also suggested many policy response options to reduce the risk of future zoonotic pandemics and to “build back better", which includes raising awareness of health and environment risks and prevention, improving health governance, including by engaging environmental stakeholders, expanding scientific inquiry into the environmental dimensions of zoonotic diseases and ensuring full-cost financial accounting of the societal impacts of the disease. 

The authors have called for enhancing monitoring and regulation of food systems using risk-based approaches, phasing out unsustainable agricultural practices, developing and implementing stronger biosecurity measures and strengthening animal health, including wildlife health services. Building capacity among health stakeholders to incorporate environmental dimensions of health, and mainstreaming and implementing one health approaches, are other recommendations. 

"To prevent future outbreaks, countries need a coordinated, science-backed response to emerging zoonotic diseases. Viruses don’t need a passport. You cannot tackle these issues on a nation-by-nation basis. We must integrate our responses for human health, animal health, and ecosystem health to be effective," says Delia Grace, lead author of the report as well as a veterinary epidemiologist at ILRI and professor of food safety at the UK’s Natural Resources Institute.

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