October 28, 2011 4:00 AM EDT

Humans have always had to endure pandemics—sudden outbreaks of new diseases that infect and kill. But Nathan Wolfe isn’t the patient sort. Wolfe runs Global Viral Forecasting (GVF), a group that monitors the porous microbiological boundaries between animals and humans, with the aim of identifying emerging viruses before they start causing problems. In hotspots like Central Africa, Southeast Asia and China, Wolfe and his colleagues grab blood samples from the local wildlife, picking up “viral chatter” that might tell them where the next biothreat will emerge.

For TIME’s profile of Wolfe, photographer Brent Stirton and I followed the scientist to field sites in rural Cameroon, where GVF has worked for more than a decade. The country is changing fast—once remote villages are now connected to cities thanks to the logging roads that cut through the forest. Those roads play a role in the spread of disease—new viruses that might have once burned out in the forest can make it to cities, and from there to the rest of the world.

And there’s no shortage of opportunities for transmission. Wolfe works with bushmeat hunters who take wild animals from the forest. Bushmeat is virtually the only source of protein in this desperately poor part of a desperately poor country, but it comes with risks. Viruses can pass between animals and hunters during the bloody process of killing and butchering. Bushmeat presents a risk to the entire planet, but it’s also a way of life in the villages. So GVF compromises—local staff members like Joseph Diffo help educate Cameroonian hunters, informing them of the potential risks and the ways to protect themselves.

Meanwhile the hunters themselves are a valuable source of information. Each carries filter paper that allows them to store drops of blood from the animals they hunt—blood that GFV scientists can screen for new viruses. The hope is that if a dangerous new virus is brewing—a new HIV or SARS—GVF might catch it early, and help stop a pandemic before it begins. “It’s as if there is a lottery going on, and the odds are getting better and better for the microbe,” says Wolfe. “And the stakes are getting higher and higher all the time.”

Brent Stirton, a 39-year-old South African, is the senior staff photographer for Reportage by Getty Images, New York. His work has appeared in publications such as National Geographic Magazine, The New York Times Magazine and Paris Match. More of his work can be seen here.

Bryan Walsh is senior writer at TIME. Find him on Twitter at @bryanrwalsh. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.

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