A fresh outbreak of monkeypox in Europe and the United States in recent weeks isn’t just a threat to public health. It’s also a warning sign.
More and more dangerous viruses, having evolved in animal populations, are jumping to the human population. Bird flu. MERS. SARS-CoV-1. And of course SARS-CoV-2, which has killed 6.3 million people since the very first infection in Wuhan, China, 30 months ago.
It’s not hard to see why these animal-to-human “zoonotic” viral outbreaks are getting more severe and more frequent. We’re chopping down more of the forests where animals live, exposing them to us and us to them. Climate change and the illicit wildlife trade only make the problem worse.
As deforestation surges, so does the risk of viral outbreaks. “The combination of climate change, population density and urban expansion is worrisome because I think we will continue to see novel viruses with the capacity to cause human disease,” said Stephanie James, the head of a viral testing lab at Regis University in Colorado.
The ongoing outbreak of monkeypox, which causes fever and a painful rash and is fatal in about one out of a hundred cases, was first noticed in the United Kingdom in early May. It seems a U.K. resident contracted the disease while traveling in Nigeria, where the monkeypox virus is endemic in rodent and monkey populations.
Despite its name, authorities haven’t determined exactly which animal started it. The previous monkeypox outbreak in the U.S., back in 2003, began with a shipment of pet prairie dogs from Ghana to Texas.
Transmitted via spittle or sexual contact, the pox has quickly spread across Europe, Australia, South America, and the United States. Health authorities have tallied around a hundred cases so far. No one has died yet in the current outbreak, but that could change as the individual infections progress.
Compared to the novel coronavirus, however, monkeypox is a walk in the park. For starters, the pox isn’t nearly as contagious as Covid. “It just doesn’t hang in the air like SARS-CoV,” James explained. And since monkeypox is related to smallpox, our vaccines for the latter can prevent the former.
As far as the pox goes, “there is still a reasonable chance to contain these outbreaks,” said Lawrence Gostin, a Georgetown University global-health expert.
What worries many epidemiologists is what happens next. As bad as the double-whammy of Covid and the pox has been, future viral outbreaks might be even worse. And if current trends continue, they’re all but inevitable.
That’s because land-clearing for crops, ranches and cities is accelerating, especially in Brazil, where rightwing president Jair Bolsonaro has undermined enforcement of environmental laws. The world lost around 15,000 square miles of forest annually for several years now, compared to 10,000 square miles in 2011. Every year we chop down an area of forest the size of Cuba.
All that deforestation not only puts workers in close contact with exotic species and their equally exotic diseases, it also sends animals fleeing into suburbs and cities in search of shelter and food, compounding the disease risk. It gets worse when you factor in the illicit trade in wildlife for meat and pets.
“We find that the increases in outbreaks of zoonotic and vector-borne diseases from 1990 to 2016 are linked with deforestation,” a team of scientists led by Serge Morand from Montpellier University in France wrote in a 2021 study. The worst outbreaks occurred in Brazil, Peru, Bolivia, the Democratic Republic of Congo, Cameroon, Indonesia, Myanmar and Malaysia, the study found.
It’s obvious the problem didn’t get better after 2016, the last year Morand’s team studied. The novel-coronavirus seems to have leaped from either bats or pangolins to human beings, possibly at a wildlife market in Wuhan some time in late 2019.
A team of researchers led by Xiao Xiao from China West Normal University identified dozens of protected species at the market, including snakes, birds and rodents. Many of the animals were obviously trapped in countries near China. Myanmar, for one. A country that, not coincidentally, is being rapidly deforested.
The nightmare scenario is a virus that’s worse than SARS-CoV-2–either more contagious or more deadly or both–making the jump from animals to people and causing a pandemic even more devastating than the current one.
And it’s not a one-way street. Zoonotic viruses can leap from animals to humans then back to animals and back to humans, mutating with each jump. This “reverse zoonotic transmission” is bound to produce ever-deadlier viral variants, said Paul Anantharajah Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection in Singapore.
It’s past time to start sampling animal populations to try and identify which viruses pose the greatest threat. “I think that we should really be looking at the idea of ‘nightmare’ viruses, in terms of zoonotic viruses that we have yet to encounter,” James said.
But preventing that pandemic requires more than just surveillance. As long as we keep chopping down the Earth’s forests and exposing ourselves to the animals who call those forests home, we’re going to continue catching those animals’ viruses. It’s a matter of when, not if, another one of those viruses goes global.