This interview was originally broadcast on Oct. 11, 2011. The Viral Storm will be published in paperback on Oct. 16.
The New Yorker once called virologist Nathan Wolfe "the world's most prominent virus hunter." Wolfe, the director of the Global Viral Forecasting Initiative, spends his days tracking emerging infectious diseases before they turn into deadly pandemics.
In The Viral Storm, Wolfe describes how most of those emerging infectious diseases originally start out in animals before making the jump to us.
"Almost all of them start from an animal virus, an animal microbe that jumps over to humans," says Wolfe. "That's actually the same with most of the major diseases of humanity. These things actually start with animals."
In Central Africa, where Wolfe has worked for over a decade, hundreds of thousands people still hunt and consume tropical wild game, called bush meat. The practice has allowed viruses like HIV to leap from wild animals to humans — and then spread rapidly across populations.
Wolfe and his colleagues in the region stress the health hazards of bush meat. But he tells Fresh Air's Terry Gross that it's difficult to change hunters' behavior without providing alternative sources of protein.
"We're actively working to come up with animal protein solutions," he says. "There are organizations around the world that we're in active discussions with on ways we can introduce novel sources of animal protein that will allow people to have different sources protein so they're not forced to hunt animal game. But most of our mission is to understand what's crossing over [from animals to humans] and to catch it early."
Wolfe regularly receives dried blood samples from animals and hunters in the region. The blood spots are taken to a lab, where they provide a quick map of the viruses that are in each region that can potentially to jump to humans.
"We see new things all the time," he says. "We see new retroviruses out there — which is the category that HIV falls into — and we're very, very concerned because this is the part of the world where HIV jumped from chimpanzees to humans. There's no reason why other viruses in that same class won't have the capacity to leap to humans ... We've found new species of malaria ... and we're really starting to burn through this massive collection of blood spots to determine just what's out there."
Wolfe also recently traveled to Asia, where the first cases of the H5N1 flu were spotted several years ago. H5N1 has killed hundreds of people around the world since it re-emerged in 2003.
The original strain of H5N1, explains Wolfe, jumped directly from birds to humans. Other viruses, meanwhile, make the leap to domestic animals before infecting humans; that mixing can then introduce deadlier strains of unknown viruses into the world.
"So what happens is you have a particular pig out there and it could get infected with two different viruses — maybe one that's been in human and one that's been in the original reservoir of a bird — and they can mix and match their genes and create mosaic daughter viruses that will have completely novel properties," he says.
That's where things can get particularly deadly. Wolfe says he thinks of viruses as having two dials: one for how transmissible they are and one for how deadly they are. The H1N1 virus, which spread to over 200 countries in 2009 and 2010, is considered to be extremely transmissible — but not extremely deadly. Meanwhile a different strain of bird flu — the H5N1 — is incredibly deadly but didn't spread as effectively as the H1N1 strain. Wolfe's team tracked people who had H1N1, but he says they were more interested in people with the deadlier strain.
"And the reason why was because we were really scared that these H5 and H1 viruses would come together in a particular human or pig and create one [virus] that was off the [transmissible and deadly] dials," he says. "And that's of course the devastating pandemic we're trying to avoid."
He points to HIV, which existed for decades before humans first became aware of it.
"Are we willing to live in a world just waiting for [viruses] to go global before we catch them?" he says. "I think that's one of the things we're trying to change. ... The earlier we detect these things, the more we have the potential to save lives in the future."
On the first person thought to have developed the H5N1 avian flu. Patient Zero was a young boy named Captain who lived in a small village in northern Thailand where he helped his grandfather care for their family's chickens.
Wolfe: "That year, a number of chickens had died. And [Captain] wanted to help out with the tasks and he carried some of the sick chickens during the outbreak that they had. A few days later, he came down with quite a severe illness ... and sadly he died. He was the first death that country had from H5N1."
On pandemics increasing in frequency
Wolfe: "If you look now [at air traffic maps] you see basically a plate of spaghetti. There are incredible connections — airlines and boats are moving humans and animals around the globe. The features of globalization have huge consequences on pandemics. It just connects us so much more closely. ... And as a consequence, every one of these viruses that passes from animals to humans has the capacity to infect all of us."
On what lives on your body
Wolfe: "If we were to count the number of cells between the top of your head and the socks on your feet, we would find that 90 percent of those cells are not human cells. Ninety percent of those cells belong to various microorganisms that exist, primarily in your gut and on your skin but also in many, many parts of your body. There's tons and tons of microbes out there."