Emerging human diseases — including not just covid-19 and SARS, but also AIDS, Ebola and Marburg — don’t arise spontaneously in humans. Instead, they are animal diseases (so-called zoonoses) that jumped from an animal host to humans. They come to us mainly from other mammals, our closest animal relatives. The reason is straightforward: A microbe evolves to be adapted to the internal chemical environment of its host and finds it easiest to jump to a new host if that host‘s internal chemical environment is similar to the chemical environment of its old host. Humans are mammals, so most zoonoses spring from other mammals.
The jump of SARS to humans occurred in wild animal markets in China. Throughout China, there are many such markets, where wild animals that have been killed or captured are sold, dead or alive, for food and other purposes. SARS came from marketed civets, small carnivores that in turn had contracted SARS from bats.
Wild animal markets exist in other countries besides China. But Chinese markets are especially efficient for launching epidemics because China has the world’s largest human population and is increasingly connected by cars, planes and high-speed trains.
These facts about the animal origins of emerging human diseases, and about the ideal transmission opportunities offered by Chinese wild animal markets, have been familiar to public health workers for many years. When SARS emerged from the markets in 2004, that should have been a wake-up call to China to permanently close the markets. But they remained open.
When a novel coronavirus surfaced in the city of Wuhan in December 2019, public health officials quickly suspected that it came from a wild animal market there. That hasn’t been proved yet, but everything points to wild animals and their trade as the source.
The Chinese government reacted initially by playing down the outbreak’s significance. But then Beijing reacted forcefully, establishing systems to limit transmission on a scale the world has never seen before. The policy appears to have helped dramatically. China also sought to prevent the emergence of more zoonoses by finally closing the wild animal markets and putting a permanent end to the trade in wild animals for food.
That’s the good news. But there’s also bad news. The government has not banned the other major route of human/wild-animal contact in China: the trade in live animals for the purposes of traditional medicine. This trade encompasses many animal species and is patronized by enormous numbers of people. For instance, the scales of small ant-eating mammals called pangolins are used by the ton in traditional Chinese medicine, because they are thought to combat fevers, skin infections and venereal diseases.
For Western observers, the solution seems obvious. How could the all-powerful Chinese government, capable of locking down millions of people within days, not prohibit the wild animal trade completely? But wild animal products represent more than a mere delicacy for many Chinese — using them is a fundamental cultural practice. But the global threat from coronaviruses is too great. China and other governments around the world must act quickly and decisively to end the wild animal trade.
Unless that happens, we predict with confidence that covid-19 will not be the last viral pandemic. There will be others, as long as wild animals are widely exploited for food and for other purposes, whether in China or elsewhere.
The world got off relatively “easily” with SARS: It killed fewer than 1,000 people, compared with seasonal influenza, which globally kills hundreds of thousands each year. Covid-19 has already killed more than 5,000 people. Regardless of the ultimate death toll, it has already staggered the global economy and will adversely impact the lives and livelihoods of millions, if not billions.
The next virus after covid-19 could do much more damage. The connectivity of the world’s populations continues to grow. There’s no good biological reason future epidemics wouldn’t kill hundreds of millions and drive the planet into an unprecedented, decades-long depression.
Such a risk would be greatly reduced by ending the trade in wild animals. That wouldn’t just be a case of the Chinese government doing a favor for the rest of the world. It would especially benefit the Chinese people themselves — because, as with covid-19, they are likely to be the first victims of the next virus emerging from the wild animal trade.