But an increasing number of health professionals and organisations believe there is a public policy model to reduce this circumstantial risk, a preventive approach known as “One Health”.

It is a public health strategy that recognises the growing threat from new animal viruses is linked to human economic expansion and taps the combined expertise of livestock and wildlife veterinary surgeons, conservationists and ecologists, along with medical doctors and researchers, to tackle it.

“It’s the preventive medicine perspective – stopping problems earlier, rather than dealing with the consequences,” said Steve Osofsky, a professor of wildlife health and health policy at Cornell University.

In the case of the Nipah virus, one preventive method is to build pig pens away from orchards frequented by flying fox bats. Another is to reduce human destruction of forests, which is thought to have driven more virus-carrying bats into orchards before the outbreak in Malaysia.

“Nipah was a turning point,” said Latiffah Hassan, a professor in veterinary public health and epidemiology at the Universiti Putra Malaysia.

“People recognised the interconnection between what’s happening in the ecosystem – land use change, agriculture intensification, and climate changes at the time – and how those all occurred at the same time, and what arises from that is something that’s very explosive,” she said.

But the approach demands that different fields of expertise and government departments work together, which can result in bottlenecks caused by politics and bureaucracy, according to professionals working on One Health programmes.

Yet, the tragedy of the current outbreak shows much needs to be done to combine and use all the knowledge available to protect humankind from the next epidemic, they say.

In practice, that means recognising, managing and monitoring the risks that have caused infectious diseases to emerge from wildlife at an unprecedented rate in recent decades.

These include changes in how people use land, like forests being ploughed into farmland; suburbs and cities spreading into rural areas; the increasing scale of the livestock industry and a booming wildlife trade – activities that drive increased contact between people and animals.

Osofsky was among the scientists who organised an international conference in 2004 that would help to lay the foundations for a formal One Health model.

The timing of the One World, One Health conference, which drew about 150 experts from around the world, was not accidental. It came on the heels of a number of disease outbreaks that followed Nipah virus: West Nile virus in New York City, severe acute respiratory syndrome (Sars) in southeastern China, and avian flu across East and Southeast Asia.

“The public health groups and the veterinary groups, they weren’t doing basic information sharing, and it took a string of these zoonotic outbreaks to force the issue,” he said. “There was almost a sense of relief that we were saying that it’s not only OK for these disciplines to be collaborative. It’s imperative.”

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Fast forward 16 years to the current pandemic, likely caused by contact between humans and animals through the wildlife trade, and these same issues of human, animal and environmental health are at play.

Some of those issues concern the sanitation and hygiene in so-called wet markets, where live and butchered wild animals and poultry are crammed next to each other, creating prime opportunity for the viruses they carry to combine, mutate and jump to people.

Others focus on the risks of China’s massive animal breeding farms. These are intended to take pressure off hunted wild populations, but critics say they lack proper regulations and health standards for how animals are kept, bred and vaccinated.

The coronavirus pandemic has triggered calls from scientists around the world to ban the trade of wildlife in wet markets.

But the One Health model is not just about identifying the origin of diseases such as Covid-19, the illness caused by the coronavirus. It aims to bond together specialists and pool information systems to prevent outbreaks or control their spread, according to epidemiologists.

For example, Hong Kong reported that two dogs and a cat with owners that had Covid-19 also tested positive for the coronavirus. Although there is no evidence these pets were able to spread the disease, it raised concerns about how to monitor such cases.

“Hospitals and veterinary departments work very separately and use separate data management systems that are not usually linked,” said Peta Hitchens, a veterinary epidemiologist and senior research fellow at the University of Melbourne in Australia.

“What would help us now is if we had the data management systems in place to know how many people who have been infected [with Covid-19] have pets in their household, whether it’s cats, dogs or rodents, for example, and whether there is a real risk within the household for further spillover,” she said.

To achieve this, questions about pet ownership could be included on Covid-19 testing surveys, she suggested.

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Gregory Gray, a professor of infectious diseases from Duke University in the United States, runs the Duke One Health Network, which works on One Health-based research and training projects around the world.

Gray is calling for Covid-19 testing to be done not only in laboratory settings but in meat production facilities where animals may be more stressed and already have other respiratory diseases, potentially making them more vulnerable.

“What if [the virus] is silently causing infections and being amplified in pork or poultry production?” he said. “What if Sars-CoV-2 [the coronavirus] is silently multiplying in pigs and causing farmers to be at increased risk? We don’t know, but it’s something we would like to look at and rule out, and to do so we need to employ a One Health technique.”

In the past two decades, One Health has created more of an awareness of these intersections between human, animal and environmental health, and helped build connections across fields, experts say. But problems often arise at government levels when bureaucrats focus on protecting their own turf.

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“What [One Health] requires is linkages between government departments, and they never like that – they each have their own budgets and different power structures,” Dirk Pfeiffer, a professor of One Health at Hong Kong’s City University, said. “If you look around the world, you will see very few examples of integration.”

Pfeiffer’s view is backed up by a 2019 guide to using a One Health approach to address zoonotic disease – published by the WHO, the United Nations’ Food and Agriculture Organisation and the World Organisation for Animal Health. It found that most countries had “inadequate mechanisms” in place for collaboration among animal health, public health and environment sectors.

“In zoonotic disease events and emergencies, lack of joint preparation and established mechanisms for collaboration can result in confusion and delay responses, and can lead to poorer health outcomes,” the report said.

Even when collaboration does exist, it may not travel down to local village levels, according to Bernard Bett, a veterinary surgeon who co-leads research on emerging infectious diseases at the International Livestock Research Institute in Nairobi. That’s where there is high risk of disease crossing from animals, yet resources are scarcer, he said.

“If you go to a hospital, a medic will treat your ailment. But if they don’t understand what is happening in the environment, they will release you back home without checking about the sources of potential reinfection,” Bett said.

Meanwhile, veterinary surgeons, too, need to “raise their level of suspicion” regarding illnesses they see in animals. Increased surveillance of domestic animals is needed because they are a potential virus transmission link between humans and wild animals, he said.

Wild animals account for about 70 per cent of emerging infectious diseases in recent decades, according to the WHO.

Having vaccines for workers dealing directly with animals, as opposed to mass vaccination campaigns, could be another strategy to mitigate risks, according to Lu Jiahai, director of the One Health programme at Sun Yat-sen University in Guangzhou, southern China.

But, as the world looks to prevent future pandemics, strategies must take into account not only human, environmental and animal health, but the economic and social factors that influence them, experts say.

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“As the world’s economies have grown, demand for wildlife and wildlife-based products has only intensified, as has our appetite to create more agricultural land, whether for soy or palm oil or pick your favourite commodity – so we are continuing to deforest at a frightening rate,” Osofsky said.

“Increasing interaction between people and wildlife greatly increases the chances of viruses being able to find us.”

Finding solutions could involve evaluating the true cost of that risk – such as budgeting in the public health costs of increased malaria or disease spillover risk – for activities including deforestation.

Such considerations fall within “planetary health”, a more recent concept stressing recognition of linkages between environmental change and public health, which Osofsky was involved in pioneering.

The impetus to change and better manage the human behaviour that drives this risk could be the “painful silver lining to the Covid-19 outbreak”, he said. “If we can’t change course now, given the circumstances we find ourselves in, I don’t know if we ever will.”

Additional reporting by Guo Rui