Researchers Pause Work on Bird Flu That Could Kill Hundreds of Millions

ROTTERDAM, Holland Jan. 20, 2012— -- It is the stuff of science fiction: scientists tamper with a killer bird flu virus and create something much worse. But what has been created in a Rotterdam laboratory is not fiction. It is deadly real.

So deadly that the U.S. government – which funded the Rotterdam research – asked scientists to omit key details of their research when they are published to keep the formula out of the hands of bio-terrorists. And today, researchers announced a self-imposed 60-day "voluntary pause" on any research involving highly transmissible form of bird flu that they have created.

The researchers are responding to the worldwide furor that erupted after word of their work became public. There are serious public health reasons for the research and they want to lower the temperature of the discussion while they explain what they have done and why they have done it.

The lead author of today's announcement is Dr. Ron Fouchier, a respected molecular virologist. He heads at Erasmus Medical Centre in Rotterdam, in the Netherlands, that engineered a form of "aerosolized" bird flu that can easily be passed from humans to humans through the air. The genetically-altered flu is thought to be so virulent that if the vials containing it were to get out, the virus would have the potential to spread around the globe and kill hundreds of millions.

Bird flu, also known as H5N1, first surfaced 15 years ago. It has not caused mass panic because it is only transmitted to humans who have direct contact with infected birds. But when humans do contract bird flu, they are likely to die.

According to the World Health Organization of 573 confirmed bird flu cases in humans since 2003, 336 people have died. That's a staggering 60 percent mortality rate. Nothing in history comes close to that.

ABC News was given an exclusive inside look at some of the testing facilities the Rotterdam researchers used. With Fouchier as our guide, we donned protective clothing and face masks and passed through three levels of security to see the ferrets he uses for testing.

Watch Jeffrey Kofman's exclusive report from inside the testing facilities tonight on "World News with Diane Sawyer," at 6:30 p.m. ET

Fouchier explained how his lab assistants exposed the ferrets to the altered virus and placed unexposed ferrets in cages nearby. All 40 ferrets died. Scientists use ferrets because they have a respiratory system much like humans, which is why the researchers believe the consequences of an airborne bird flu would be just as deadly for humans.

No visitors, however, allowed in the high secret lab at Erasmus Medical Centre where the actual experiment took place. He told us that with U.S. and Dutch expertise Erasmus spent eight years and millions of dollars building one of the most secure lab facilities in the world just for studying H5N1. They call it a BSL3 Enhanced lab – that's Bio-Safety Level 3. The vials of enhanced bird flu are kept in a bank vault inside the lab. The lab is designed to keep the deadly virus in and intruders out.

The researchers who engineered this super-virus insist they are far from being "mad scientists" as some have suggested. They are public health specialists.

The man in charge, Fouchier is a tall, lanky molecular biologist who began his career studying HIV in Philadelphia, but switched to bird flu when the mysterious virus first surfaced in 1997.

"What scares me is that this can happen so easily," he says, "it's scary that it might actually happen in the field."

And that's the point behind research that on the surface seems insane to some. Fouchier says what he did in the lab was mutate a few genes. That happens regularly in nature.

Fouchier insists the dangerous part of this virus isn't what he has created in the lab, it is what can happen if nature creates something similar. He says this should be a wakeup call for public health authorities around the world.

In the history of epidemics and pandemics nothing has been as lethal as the bird flu Fouchier has created. The most deadly epidemic of the last century was the Spanish Flu outbreak of 1918. Virtually everyone in the world was infected. It is estimated that between 50 and 100 million people died -- conservatively that means it killed 3 percent of those infected. In a globalized world of air travel and mass transit, the prospect of an airborne bird flu with a 60 percent death rate is terrifying.