The Lost City of the Monkey God: A True Story(85)
At the time that Dr. Bradley was investigating the disease in Oklahoma, an outbreak of cutaneous leishmaniasis occurred in northeastern Texas and in a string of suburbs in the Dallas–Fort Worth metro area; the dozen or so victims included a little girl who had lesions on her face, and in one case a cat and a human in the same household got the disease. Doctors in the health departments of Texas and Oklahoma joined forces to track the source. They were especially worried because none of the victims had traveled: They had gotten the disease in their own backyards.
Dr. Bradley led the investigation of the two cases in Oklahoma. She assembled a team that included an entomologist and a biologist. When the team visited the patients and surveyed their properties, they noted burrows of wood rats and populations of sand flies, which they concluded must have been the host and vector. The investigators trapped a number of rats and sand flies and tested them for leish. None had the disease, but by this time the mini-outbreak had died down.
I called Bradley and asked if the leish had really died out or if it was still around. “I’m sure it hasn’t gone away,” she said. “It’s smoldering somewhere out there, quietly cycling in nature,” waiting for the right combination of circumstances to break out again. When she and her team mapped leish cases in the United States over time, they revealed an inexorable spread northeastward across Texas and Oklahoma, aiming for other states in a northeasterly direction.
Why?
Her answer was immediate: “Climate change.” As the United States becomes warmer, she said, the ranges of the sand fly and the wood rat are both creeping northward, the leish parasite tagging along. The sand fly genus known to spread this kind of leish has now been found in the United States five hundred miles northwest and two hundred miles northeast of its previously established range.
A recent study modeled the possible expansion of leishmaniasis across the United States over the next sixty-five years. Since it takes both vector and host to spread the disease, the scientists wanted to know where the sand fly/wood rat combination would migrate together. They looked at two future climate scenarios, best case and worst case. For each case, they extrapolated out to the years 2020, 2050, and 2080. Even under the best-case climate assumptions, they discovered that global warming would push leishmaniasis across the entire United States into southeastern Canada by 2080. Hundreds of millions of Americans could be exposed—and this is just by wood rats. Since many other species of mammals can host the leish parasite—including cats and dogs—we know the potential problem is far greater than what was described by this study.* A similar spread of the disease is expected in Europe and Asia.
It seems that leishmaniasis, a disease that has troubled the human race since time immemorial, has in the twenty-first century come into its own. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the NIH, told our team bluntly that, by going into the jungle and getting leishmaniasis, “You got a really cold jolt of what it’s like for the bottom billion people on earth.” We were, he said, confronted in a very dramatic way with what many people have to live with their entire lives. If there’s a silver lining to our ordeal, he told us, “it’s that you’ll now be telling your story, calling attention to what is a very prevalent, very serious disease.”
If leish continues to spread as predicted in the United States, by the end of the century it may no longer be confined to the “bottom billion” in faraway lands. It will be in our own backyards.
Global warming has opened the southern door of the United States not just to leish but to many other diseases. The big ones now entering our country include Zika, West Nile virus, chikungunya, and dengue fever. Even diseases like cholera, Ebola, Lyme, babesiosis, and bubonic plague will potentially infect more people as global warming accelerates.
Modern travel has given infectious disease new ways to spread. Bubonic plague in the fourteenth century traveled from Central Asia to the Levant and Europe by horse, camel, and boat; the Zika virus in the twenty-first century jumped from Yap Island in Micronesia to French Polynesia, Brazil, the Caribbean, and Central America by 2015, all by plane. In the summer of 2016, Zika arrived in Miami, again on an airplane. The 2009 outbreak of deadly H1N1 swine flu in Mexico hitched rides on planes to strike as far away as Japan, New Zealand, Egypt, Canada, and Iceland. As Richard Preston noted in his terrifying book The Hot Zone, “A hot virus from the rain forest lives within a twenty-four-hour plane flight from every city on earth.”
The world’s last great pandemic was the Spanish flu outbreak in 1918 that killed a hundred million people—about 5 percent of the world’s population. If a pandemic like that were to happen again, it would spread faster and might be impossible to contain. According to the Bill & Melinda Gates Foundation, in such a pandemic “the death toll could reach 360 million”—even with the full deployment of vaccines and powerful modern drugs. The Gates Foundation estimated that the pandemic would also devastate the world financially, precipitating a three-trillion-dollar economic collapse. This is not scaremongering: Most epidemiologists believe such a pandemic will eventually happen.
Archaeology contains many cautionary tales for us to ponder in the twenty-first century, not just about disease but also about human success and failure. It teaches us lessons in environmental degradation, income inequality, war, violence, class division, exploitation, social upheaval, and religious fanaticism. But archaeology also teaches us how cultures have thrived and endured, overcoming the challenges of the environment and the darker side of human nature. It shows us how people adapted, lived their lives, and found fulfillment and meaning under fantastically diverse conditions. It tracks both the failures and the successes. It tells us how cultures faced difficulty and challenge, sometimes in successful ways and sometimes in ways that, while successful at first, sowed the seeds of eventual collapse. The Maya created a vibrant and brilliant society that, in the end, failed to adjust to a changing environment and the needs of its people; so did the Roman Empire and the ancient Khmer, to pluck civilizations randomly out of the hat. But the people of the City of the Jaguar did adapt to the challenges of the rainforest, and they continued to thrive in one of the harshest environments on the planet, transforming it into a beautiful garden—until their abrupt demise.