When should scientists stay schtum?

Fears over terrorists creating weapons from highly deadly form of bird flu.

The doomsday plot of The Satan Bug, with Anne Francis and George Maharis, has now come worryingly close to reality. Courtesy Everett Collection

As the basis for a Hollywood movie, the storyline of Alistair MacLean's 1962 thriller The Satan Bug takes some beating: scientists modify a virus to make it so infectious it could devastate the human race in a matter of months - and it falls into the hands of a maniac.

Exactly 50 years on, the plot of The Satan Bug has now come worryingly close to reality. So close, indeed, that the scientific community is convulsed with controversy over whether the details of the research should ever be published, lest terrorists use it for their own evil ends.

The concern centres on the so-called avian flu H5N1 virus, which caused panic in 2005 when it spread like wildfire among bird populations worldwide.

Barely 100 humans became infected - but of those, almost half died, making the virus one of the most deadly known.

At the time, scientists warned that only the low human infectivity of the virus was preventing it turning into a global killer on a scale of the notorious Spanish flu virus pandemic of 1918-20, which claimed at least 50 million lives.

That terrifying combination of lethality and infectivity has now been brought closer to reality by two international teams of scientists, who have combined H5N1 with another variety similar to the one responsible for Spanish flu.

At least, that's what they are thought to have done; it's hard to be sure as their papers are currently being sat on by two top science journals, because of fears it would give terrorists a 21st-century Satan Bug.

It should be stressed that the scientists carried out the study for the best possible reason: to understand the risk of the H5N1 virus mutating into a far more infectious form.

Many virologists want to see the results published, as it could help surveillance teams spot outbreaks of the pandemic variant earlier - with obvious benefits for the world.

But following a similar scare in 2003 about research into anthrax, the world's top science journals have made it plain that they may censor research that could attract unwelcome attention.

Now, following a meeting organised by the World Health Organization, both research reports will be published in full later this year.

But advocates of academic freedom would do well to remember a strikingly similar dilemma that was resolved in the same way - but with results that could easily have proved disastrous.

Its origins lie in a revelation that occurred to a Hungarian physicist named Leo Szilard one September day in 1933.

Standing at the junction of two busy roads in Bloomsbury, central London, Szilard realised that some chemical elements might be persuaded to take part in an explosive "chain reaction".

The idea was simple: fire sub-atomic particles called neutrons at the heart of a chemical element, and force it to split apart.

Then, if the right chemical element was used, the resulting fragments would have a lower mass than the original element, the surplus being released as energy via Einstein's famous formula E = Mc2.

Crucially, these fragments might also be accompanied by more than one neutron for each one that hit its target. These would then fly off, triggering yet more splittings, neutron and energy release in turn, producing a rapid chain reaction - and a huge explosion.

Szilard immediately realised that this could potentially be the basis of a weapon of mass destruction. He was also aware that there could be disastrous consequences if this fell into the hands of the Nazis, then seizing power in Germany.

What he didn't know was whether a suitable chemical element existed. When the answer emerged in 1938, it came from a worrying source: two scientists based in Berlin, who had discovered that uranium might sustain a chain reaction.

Whether it actually would depended on the neutrons released, and Szilard set about finding out more. He quickly discovered he was not alone: the great Italian-American physicist Enrico Fermi was also on the case.

They both found evidence suggesting a chain reaction was possible, but fearful of tipping off the Nazis, Szilard and Fermi agreed to send their results to a leading journal but request publication be delayed until they could gauge the nature of the Nazi threat.

But their caution proved pointless. In early 1939, with the Nazi war machine moving into top gear, Szilard learned that scientists in Paris were on the brink of performing the same key experiment.

He wrote to the head of the group, the Nobel Prize-winning French nuclear chemist Frédéric Joliot-Curie, warning of how their work might put "exceedingly dangerous" weapons in Nazi hands.

The Paris team pressed on, and confirmed that a chain reaction was possible. Now Joliot-Curie and his colleagues faced a choice. They could either advance their careers by publishing this historic result in a journal, or they could keep it under wraps and out of reach of the Nazis.

Unlike Szilard and Fermi, they blithely sent their results to Nature, the world's most widely read science journal, even describing their results in terms of "the nuclear explosion of uranium".

Sure enough, within days of the paper appearing, two German physicists informed the Nazi War Office of research pointing to "an explosive many orders of magnitude more powerful than the conventional ones", adding: "The country which first makes use of it has an unsurpassed advantage over the others".

Within a week, the Nazis began their own nuclear research programme and had banned exports of uranium from the mines it had seized in Czechoslovakia. Japan, too, started its own research programme.

Fortunately, the Nazis' scientists made blunders that prevented them turning Joliot-Curie's research into an atomic bomb. The Japanese made more progress, but abandoned the programme after realising the colossal expense involved in making such a bomb.

Until the virus research is published, the difficulty of turning H5N1 into a weapon will remain unclear. But we should all be concerned about ever again relying for our protection on the incompetence or impecuniousness of those who would do us harm.

Robert Matthews is visiting reader in science at Aston University, Birmingham, England