The Next Lethal Disease to Sweep the Planet Could Be Lurking in the Amazon

The Amazon basin has all factors that can generate new “zoonotic” diseases, and on a scale unprecedented in human history.
The red dust of the BR230 highway, known as "Transamazonica", mixes with fires at sunset in the agriculture town of Ruropolis, Para state, northern Brazil, on September 6, 2019.

LIMA, Peru — At first the young farmer from the village of Samuzabeti, deep in the Bolivian Amazon, had fever and a headache. A few days later, his bones were throbbing in pain. Then he started vomiting blood.

Within two weeks, the previously healthy 22-year-old was dead.

Doctors analyzing samples from his cadaver identified the cause of this strange Ebola-like sickness as a previously unknown member of the arenavirus family. They named it the Chapare virus, after the sweltering, coca-growing region where Samuzabeti is located.


Since that small outbreak in January 2004, the pathogen has not been seen or heard from again, at least not by the scientific community. Yet it is almost certainly still lurking out there, in an unknown host species.

Why the novel coronavirus resulted in a world-stopping pandemic while the Chapare virus petered out after claiming a single life is a complicated tale involving a series of biological, geographical and human factors.

But the case highlights the growing risk that the next lethal disease to suddenly sweep the planet could emerge from the Amazon, the world’s largest and most biodiverse rainforest, as humans increasingly upset its fragile ecological balance.

When it comes to the factors that can generate new “zoonotic” diseases—which originate in animals but then jump the species barrier to humans—the Amazon has them all, and on a scale unprecedented in human history; massive deforestation, humans increasingly occupying degraded tropical ecosystems to log, mine, dam, build roads, hunt, ranch and farm, and weak government institutions unable to enforce environmental laws.

The Amazon basin also has great diversity in the three most risky animal groups: bats, rodents and primates. And it is also host to “wet markets”, like the one in Wuhan, where the current pandemic is thought to have originated.

There is also one other significant danger — the Amazon’s legendary biodiversity translates into extremely high virus diversity thanks to the myriad of host species.


“When you shake up an ecosystem, things fall out,” says Christopher Walzer, a veterinary professor who heads the Wildlife Conservation Society’s health program. “The Amazon has many of the right ingredients. There is a huge risk.”

The next outbreak in South America will likely be another hemorrhagic fever, like Ebola, warns Carlos Zambrana-Torrelio, an evolutionary biologist at the EcoHealth Alliance, which works to prevent new pandemics.

“Each country in the Amazon has new diseases appearing regularly,” he adds. “People are already falling sick. But they are usually doing so in remote, frontier areas. Epidemiologists often never find out.”

“Zoonotic” infections are hardly new. Six out of 10 of all known diseases are zoonotic. They include everything from rabies to salmonella and Lyme disease. New ones have been popping up around the globe at a rate of about two a year for the last century, although that is now gently accelerating as humans decimate more and more natural landscapes.

The EcoHealth Alliance, whose funding from the U.S government was cut by President Donald Trump earlier this year, has set up a database of the most potentially dangerous such “emergence events”, including the Chapare virus.

Yet even since the advent of Covid-19, the Amazon has been flying largely under the radar of many scientists, who have been concentrating their research on potential new pathogens on Asia and, to a lesser extent, Africa. Nevertheless, the risk factors are subtly distinct in the Amazon from those in Southeast Asia.


Nowhere in the Amazon is there a city comparable in scale or global connectedness to Wuhan, which has 11 million residents and, before international flights were grounded, saw hundreds of people flying to and from New York each day.

The Amazon's wet markets are also different. Most, but not all, of the animals there have already been butchered, reducing — but not eliminating — the risk of spillover when animals are slaughtered in the market, splashing other species, with whom they would not naturally have come into contact with blood, urine and excrement.

Eating bats is also largely taboo in South America. And while consuming exotic wildlife in China is now often a luxury reserved for the more affluent, in South America it is both a tradition and a necessity for the poor, making it unrealistic to simply ban – rather than regulate — the practice here.

The highest risk comes at the frontier between deforested land and surviving jungle, where humans live or work next to or within damaged ecosystems, sometimes carved up into small islands of dense vegetation scattered amid fields. Here, surviving wild species frequently rub shoulders with each other in a way that does not happen in untouched wilderness.

“One of the worst things you can have is livestock in a small clearing in the forest, especially if you have humans, perhaps a family, living right there,” says Walzer.

In these kinds of degraded areas of forest, well-known zoonotic diseases, such as malaria and yellow fever are already surging.


Dionicia Gamboa, a malaria researcher at Peru’s Cayetano Heredia medical school, says that if funding to research the disease, which killed more than 400,000 people in 2018, is limited, it should not be surprising that scientists are struggling to raise cash to detect new, previously unknown germs.

“Because malaria doesn’t kill in Peru the way it does in Africa, it doesn’t get much attention,” she says. “But it still has huge impacts. People get sick. They can’t work or go to school. And we are usually talking about the poor.”

Currently, the World Health Organization is monitoring potential threats in the Amazon through an organization called PANAFTOSA, originally set up in the 1950s to prevent foot-and-mouth disease. It is focused on livestock rather than wildlife or ecoystems, and is largely dependent on the political will and technical capacity in each Amazon nation. “We didn’t see Zika or Chikungunya coming,” admits researcher Ana Riviere-Cinammond.

Zambrana-Torrelio cites Brazil, Venezuela and Bolivia, his own country, as three nations that have done little to anticipate new diseases coming out of the rainforest. He says that the only country in the world that has set up an early warning system that focuses on animal, environmental and human health simultaneously is Liberia, which went through a devastating Ebola outbreak from 2014 to 2016.

Avoiding these risks, in the Amazon and elsewhere in the tropics, would be expensive. Researchers have calculated that taking all the necessary steps to reduce deforestation, set up a global zoonotic early warning system, crack down on illegal wildlife trafficking and implement better farming standards would have a net cost of between $18 billion and $27 billion per year.

That sounds like a lot. But the same researchers also estimated that the current pandemic, in addition to all the lives lost or shattered, is likely to cost $5 trillion just in 2020.

Cover: The red dust of the BR230 highway, known as "Transamazonica", mixes with fires at sunset in the agriculture town of Ruropolis, Para state, northern Brazil, on September 6, 2019. Credit: JOHANNES MYBURGH/AFP via Getty Images.