Earlier this month, the scientists who altered the H5N1 virus to create a more contagious strain that's transmissible between ferrets, agreed to a temporary moratorium, due to safety concerns. The NewsHour reported the story here and here.

That decision has, if anything, intensified the debate. What began as a question on whether scientific journals should publish the complete research has grown into an argument on whether to conduct these studies, and others like them, at all.

The Newshour asked three experts to weigh in on the matter: Richard H. Ebright, a molecular biologist at Rutgers, Vincent Racaniello, a microbiologist at Columbia, and Carl Zimmer, a journalist who has authored ten books about science, specializing in biology and evolution.

Answers have been edited for length.

What were the goals of either the Wisconsin or Dutch bird flu studies?

Zimmer: We know that sooner or later, new kinds of diseases hit our species. You just have to look at history--the way SARS appeared out of nowhere in 2003, for example. HIV crossed over from chimps to humans in the early 1900s, but no one even knew about it until the 1980s. That head start allowed HIV to become one of the most horrific killers of the twentieth century.

The only way to prepare for new outbreaks is to study dangerous viruses in the lab--and, in some cases, even make them from scratch.

There's been a lively debate about just how big of a risk H5N1 poses to humanity. It normally passes from bird to bird. When it manages to infect humans, it seems to be quite deadly. Flu viruses are continually evolving, adapting to their hosts, and yet H5N1 has not managed to spill over into our species for years now. That might mean that there are too many obstacles in the evolutionary landscape for H5N1 to reach a form that would allow it to become a human-to-human pathogen. The studies in Wisconsin and the Netherlands were designed to address that question.

Racaniello: The goal was to determine if H5N1 aerosol transmission could be achieved in ferrets in the laboratory, and if so, what mutations accompany this process. Avian H5N1 viruses do not transmit among mammals, and therefore such experiments provide invaluable insight into this process.

Ferrets were used because they are a good model for influenza virus infection. When ferret-to-ferret transmission was achieved, the amino acid changes involved can provide information on the mechanisms that regulate airborne transmission of viruses, a topic that is poorly understood. Furthermore, it makes it possible to look for these mutations in H5N1 viruses circulating in the wild, to provide an early warning of the emergence of viruses that might transmit among humans. It is important to point out that ferrets are not humans, and the viruses selected in ferrets are not likely to transmit among humans.

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