No one could have predicted the timing and trajectory of the Covid-19 pandemic, triggered by a novel coronavirus leaping from a bat into a pangolin (apparently) and from there into a person. Even so, scientists knew that a pandemic of some kind would come our way sooner or later. In the past few decades, we’ve seen ever-more-frequent outbreaks of new infectious diseases, as viruses or bacteria hop from their usual animal hosts into people. After this virus, there will be others.
Outbreaks are becoming more frequent for a very simple reason: There are more people coming into contact with wildlife species, as agriculture, forestry, mining and oil exploration activities have pushed into previously unpopulated areas, destroying animals’ natural habitats. The high-risk zones for new infections turn out to lie mostly in tropical regions — where biodiversity is high — undergoing significant land-use change.
A disease caused by a virus or bacteria that originates in another animal is known as zoonosis. The word comes from the Greek: “zoo-” for animal, “-osis” for disease. Zoonotic pathogens are a persistent menace all over the world, threatening to jump into humans and spread. The first challenge is to know how many pathogens there are and in which animals they thrive, and on this, researchers are making good progress.
Much as NASA is working to give us advance warning of all the hazardous asteroids that could strike Earth, biologists are doing the same for the hundreds of thousands of unknown zoonotic pathogens living in animal hosts. It’s an expensive undertaking, yet vastly cheaper than the costs of a global pandemic. A decade long effort to find such viruses, the Predict project, came to an end just as the novel coronavirus was emerging. But the researchers collected 140,000 samples from animals and identified 1,000 new viruses. They also trained 5,000 people across Asia and Africa in crucial skills, such as how to collect samples from wild and domestic animals, thereby creating new resources of expertise in zones where new viruses are most likely to appear.
Fortunately, the Predict project received an emergency six-month extension effective April 1, and its work will carry on in a follow-up project called STOP Spillover, set to begin in August. Meanwhile, researchers behind a separate scientific project — the Global Virome Project — ambitiously aim to characterize within the next 10 years most of the viruses from the most important zoonotic reservoirs. But merely listing these pathogens isn›t enough. We also face the harder challenge of reducing how often those pathogens come into contact with humans, each time having a small chance to create a new epidemic.
Everyone knows that human activities have disturbed ecosystems worldwide. Less well known is that our activities have also increased infectious-disease transmission between humans and animals. Never before have the reservoirs of potential zoonotic pathogens been in such intimate contact with human populations. A review of research on the consequences of land-use change over the past 30 years found consistent evidence of increased pathogen transmission.
The most obvious setting is in wildlife markets, directly implicated in the origins of both the SARS epidemic in 2002 and the current Covid-19 pandemic. In the former case, the virus moved from bats into civet cats, which were sold for meat in markets, and then into people. In response to any pandemic, nations often ban the sale of wild animal products, as China has now, temporarily. But such bans tend to be relaxed after the pandemic is over.
Exploitation of wildlife is the biggest threat to biodiversity in many Southeast Asian countries, with high demand for wildlife products combined with weak law enforcement. That›s a major threat to many endangered species, and also a direct threat to all of us. After Covid-19, we should realize that the only solution is international cooperation based on the shared realization that our human activities have made the pandemic problem worse. Mark Buchanan, Bloomberg
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