The Virus Hunters

With SARS breaking out in China again, the Chinese authorities have ordered the mass slaughter of animals known to carry the virus. But scientists admit they still don't where SARS is coming from – and what the original source of SARS may be.

Every year or so, a new virus seems to spring from nowhere. Along with SARS, there's been West Nile Virus, Monkey Pox, HIV and a virus you probably haven't heard of yet — a nasty killer called Nipah.

Recently, 60 Minutes II went to the Far East with a team of American scientists who are involved in a new kind of detective work; they're virus hunters looking for the next big killer.

They're finding that new viruses are leaping from animals into man in suprising ways. And there's no better example than the search for the origin of Nipah, a bug so lethal they had to build a prison to hold it. Correspondent Scott Pelley reports.

"The main feature of this laboratory is the safety. We call it complete containment, meaning anything that comes in can not go out," says Dr. Abdul Aziz, a government scientist. "Complete containment -- 100 percent containment."

Why 100 percent for Nipah virus? Well, consider this. SARS kills about 9 percent of all those it infects. Nipah kills 40 percent.

In the lab, they keep the virus-infected tissue to study Nipah, a virus that's probably been around for millions of years, but apparently never killed a man until recently. The lab is working on ways to quickly identify any future outbreak.

Why? Because they don't ever want to see what happened in 1997 again. That year, out of nowhere, people began to die. Approximately 265 people came down with terrible symptoms.

"Temperature, fever, headache, but fairly quickly, it went into a coma and unconsciousness and then people needed to be on ventilators," says Dr. Hume Field, an Australian virus expert who was alarmed by how fast people were dying. "In 48 hours or so, they could be in a coma, and certainly within a couple more days, they could be dead."

Fortunately, for the virus hunters, it turned out that the 105 people who were killed on the Malay Peninsula had one thing in common: they were all near pig farms. When Field went to the farms, he found a raging epidemic in the pigs.

"There would be this symptom associated with the disease in pigs - a barking cough and it became known as 'a one-mile barking cough' because you could hear it a mile away," says Field. "People would know that the disease had arrived in their area, and they'd hear the cough and they'd hear the cough coming closer and closer to their neighbors, and they'd know that they were going to be next."

The Malaysians pumped clouds of poison into the pig farms to kill mosquitoes, a common carrier of viruses. But the disease kept spreading. With no idea of where the virus was coming from, Malaysia crushed every pig farm in the region and slaughtered all the pigs. More than a million pigs were killed, and that seemed to do the trick.

Two years after Nipah emerged, it disappeared. But the mystery and danger remained, and scientists still don't know how the pigs got the disease.

"That's the fundamental question - where did the virus come from into the pigs," says Field.

The destination was a volcanic island called Pulau Tioman, west of Borneo, more than 150 miles from the outbreak on the mainland. This island is not very developed, but there are a few settlements along the coast. The interior of island is just pure primary rainforest.

Dr. Jon Epstein and Dr. Peter Daszak are virus hunters traveling the remote corners of the earth for the Consortium for Conservation Medicine. It's a partnership of schools, including Harvard, Tufts and Johns Hopkins, along with the U.S. Wildlife Health Center and the Wildlife Trust. It's an American program looking for viruses on the far side of the planet.

Why should Americans be worried?

"We never had Monkey Pox in America. We don't even have monkeys in America. How do these diseases pass into a place that seems completely unrelated? With the increase in global travel, with the increase in trade, with the increase in human activities all over the world, the world's becoming a small place," says Epstein.

"So just because there may not be Nipah virus in America right now doesn't mean that a similar virus can't emerge there or that other unknown diseases can't pass from wildlife into people in America."

These medical detectives are exploring places like this because most new viruses infecting man are coming from the wild.

"In fact, almost 75 percent of the emerging diseases in humans actually come from animals, wildlife or domestic animals," says Daszak. "So normally, you need to go to those wildlife species and look for the virus there."

They've come to look at Tioman Island because they suspect they'll find the animal that first carried Nipah -- the original source of the virus. Daszak told us if this kind of work was done decades ago, it might have changed the history of AIDS.

"With HIV, we are looking at a virus that emerged in chimpanzees in Africa some time in the last century. That virus emerged into one single person hunting chimpanzees. It was a single-person event. Wouldn't it be amazing to go back in time and say, 'Hey, don't butcher that animal, you're going to have a virus that goes on to kill 40 million people,'" adds Daszak, who says that's what they're hoping to prevent.

"You have to look for key things. One, often times you can hear them from a distance, so you listen carefully for the sound of the colony," says Epstein.

How big are the colonies?

"In Australia, the colonies can get up to tens of thousands of animals," adds Epstein. "The one's we're seeing on the island are considerably smaller. The one that we found here so far is about 600 - 800 animals, maybe 1,000."

60 Minutes II didn't find one on a hike. But down the coast, near the beach, there were flying foxes sleeping, shrouded in their 3-foot wings. They hang out all day and fly out only at night to hunt for food - tropical fruit like mangos. They return at daybreak.

Epstein planned to catch them by throwing up a detour on their commute. He raises an almost invisible black mesh, strung up like a too-tall volleyball net. Bagging bats turned out to be the easy part, but the hardest part was releasing them.

"They do get tangled up, but none of them get hurt in this netting process," says Epstein. "We've not lost any bats at any time. It's a very safe procedure."

It may be safe for the bat, but there's nothing the flying fox would like more than take a bite out of Epstein. Once he's caught 10 or so, he waits for sunrise and does it all again.

He shows us a young male flying fox about a year old. "They're called flying foxes because their head really does look like a fox with wings," says Epstein, who anesthetizes the bat and takes tiny pieces of wing, some blood and swabs around those needle like teeth.

What will the swab tell him?

"It's one of the places that we believe, that we actually know, Nipah is present is in the saliva. We found it in a piece of fruit that was eaten by a bat. We actually found real virus," says Epstein.

That piece of fruit - which had been chewed up by a flying fox - may be the missing link in the mystery of how a bat virus came to kill more than 100 people. Just 150 miles away from Tioman, this is where the first infections happened. And there are fruit trees over the pig pens.

"What obviously happened here was fruit bats were feeding in these trees and somehow dropping bits of fruit in the pig pens," says Daszak. "Pigs would eat them and then get infected. That's what we think happened here."

The bats didn't seem to carry enough virus to infect humans, but the pigs became virus incubators, amplifying the virus billions of times, and then coughing and sneezing on the farmers.

On Tioman, Epstein netted 72 bats in all. Of those, four tested positive for Nipah exposure. That's a little over five percent. They found the source and the path of the pathogen -- from a tiny number of bats to pigs to man.

"When we talk about wildlife diseases that jump into humans, it's a universal story. It doesn't just happen in Malaysia with Nipah virus. It happens in China. It happens in North America," says Epstein.

"By understanding some of the ecological factors that drive disease emergence, some of the factors like human activities, that bring people closer to wildlife, that place stress on wildlife, that make it more likely for these diseases to jump into humans, we hope to be able to apply these principals in general to other diseases and prevent future outbreaks."

And with a little knowledge, the solution can be simple, according to the virus hunters. Malaysian farmers are warned not to plant mangos next to pigs anymore. The Nipah outbreak ended in 1999, but since then, SARS has come to Asia and Canada, and in the U.S., people have been infected for the first time by monkey pox from Africa.

Dr. Daszak says other viruses still undiscovered are waiting as man presses into the last wild places on earth.

"What worries me the most is that we are going to miss the next emerging disease - that suddenly we are going to find a SARS virus that moves from one part of the planet to another, wiping out people as it moves along," says Daszak.

"Something like Nipah virus, where 40 percent of the people who get infected die. That's something to keep you awake at night."