Ebola, SARS, avian influenza, AIDS. In addition to being deadly and highly contagious, these headline-making diseases all followed a common pattern: they started in animals and made the leap to humans. With over 75% of emerging infectious diseases originating in wildlife, understanding and properly preventing the spread of such diseases—made increasingly likely by logging and mining in the developing world, the ease of international travel, and climate change—is one of the defining global health challenges of this century, says science writer David Quammen.
To report his new book, Spillover, Quammen followed zoonotic (transmitted from non-human animals) disease specialists into the field in Africa, Asia, and even the U.S.—where just this summer there have been outbreaks of West Nile virus in Texas, Eastern equine encephalitis in New England, and hantavirus in California. He found that the complex mechanisms underlying these diseases—and the unique public-health challenges in preventing their spread (including anti-"bush meat" public-relations campaigns)—require an increasingly cross-disciplinary response.
"There’s almost a new job description—a new kind of professional emerging," he says. "The combination of a veterinary degree, a PhD in ecology, and a masters in public health is the ideal training for this kind of work. A significant number of the people I met have this combination, or two out of the three." Quammen explains that a public health background helps with understanding the epidemiology of a disease once it's in the human population. Determining the point of actual "spillover"—where contact with diseased wildlife occurs—is an ecology problem. And veterinary training helps with understanding and searching for where infections are lurking within the animal population. It’s the merging of these three skill sets, says Quammen, that’s enabling real progress to be made.
The ability to craft culturally relevant public-education messages is another important skill in pandemic prevention. In exploring the origins of HIV in southeastern Cameroon, for example, Quammen encountered AIDS awareness posters in public buildings that, rather than warning about unsafe sex or trading needles, cautioned the populace not to eat apes. (It’s believed that HIV first jumped to humans from a chimpanzee in this region.) A certain cross-cultural diplomacy—and old-fashioned fieldwork—are also at the work in the efforts of people like Nathan Wolfe, who leads Global Viral, who has successfully engaged African wildlife hunters in helping to collect blood samples from their prey.
Advances in technology—and the contributions of a range of laboratory experts—are also beginning to have a significant impact. "It’s very difficult to predict where the next big one will come from," says Quammen. "There so much uncertainty and randomness in the way things happen. Instead of predicting, we can have fast detection and response thanks to high-tech analysis of blood samples in the lab, for example. When SARS spilled over and went to Hong Kong, Toronto, Singapore, and Hanoi, it was a good candidate to be the next ‘big one.’ It wasn’t, because we had the burgeoning ability to diagnose what the virus was quickly enough to stop it."
For those drawn to the challenges posed by spillover diseases, there’s really no end in sight—and no geographic boundaries. "Don’t delude yourself that this is a third-world problem for people in Africa who eat monkeys," says Quammen. "These kinds of diseases are as American apple pie. We’re coming into contact with animals in lots of ways—capturing them for medical purposes, exporting them as exotic pets—and moving them, and ourselves, around the world faster and faster. It’s the yin and yang of disruption and connectivity."
[Image: Flickr user Eneas De Troya]