In recent weeks, headlines have been filled with scary diseases like the hanta outbreak in the national parks out West and West Nile virus closer to home. These — as well as the nightmarish diseases Ebola, SARS and AIDS — are examples of what scientists call “spillover.”
In a spillover, a virus or other disease-causing pathogen moves from an animal species (everything from chimps to chipmunks) to human beings. Though the virus may not cause any particular problem in this animal “reservoir host,” when it reaches human beings it might cause an outbreak of a highly contagious disease with horror-movie-high death rates.
Science writer David Quammen has traveled around the world to learn about these diseases. He met with researchers in the lab and in the field, went chimp-hunting and bat-catching, and talked to survivors and other witnesses to outbreaks. He also traces their history — AIDS, for instance, spilled over from chimps to humans back around 1908.
Quammen describes his adventures in a highly readable book, “Spillover: Animal Infections and the Next Human Pandemic.” This is the first book written for the general reader that draws the connections between medicine and ecology. “Human health, the disruption of wild ecosystems, the infection status of bats and rodents and monkeys and the ecology and evolution of viruses are all inextricably connected,” he says.
On the rise
These diseases are becoming more more frequent and more fatal for three reasons:
1. The human population has reached 7 billion and is headed toward 9 billion, with many living in cities. Disease travels fast in crowded conditions.
2. Humans are destroying natural habitats as we clear land to live and grow food on. This puts us in closer contact with the animal reservoirs carrying disease.
3. Modern transportation moves viruses around the globe within days or hours.