Scientists say the H5N1 avian influenza virus has the potential to infect and spread among humans, raising the possibility of a catastrophic global pandemic. This and other findings about H5N1 were published this week in the journal Science, less than a year after their release was withheld at the request of US government and World Health Organization officials, over concerns that the information could fall into the hands of terrorists.

In a series of articles published in Science, researchers describe how the H5N1 avian flu virus is capable of jumping species and being spread by airborne transmission among mammals -- including humans.

Guided by genetic studies of the viruses that caused the virulent flu pandemics of 1918, 1957 and 1968, investigators identified the genetic changes that would be necessary for a global outbreak of H5N1. Investigators concluded that as few as five gene mutations enabled the bird flu virus to jump the species barrier and become infectious among mammals.

Derrick Smith is with the University of Cambridge England and the Fogarty International Center at the National Institutes of Health near Washington.
Smith used a mathematical model to determine whether the existing virus could naturally acquire the mutations needed to become a human pandemic threat. In a telebriefing with reporters, Smith said researchers now know that it could.

"This is a little like being in a situation where as we would all like to, for example, predict an earthquake or a tsunami. We now know that we're living on a fault line," he said. But according to Smith, it's hard to predict if or when H5N1 could strike, developing the remaining mutations or genetic substitutions in birds that would make the avian virus transmissable to humans.

Another manuscript just published in Science lays out strategies to prepare for a bird flu pandemic, including vaccinating as many people ahead of time with existing H5N1 vaccines to prime their immune systems and lessen the severity of a pandemic. Research is underway to make large quantities of a vaccine specifically against the deadly flu strain.