One, two, many . . .

When David Nabarro debuted as bird flu czar he made his first controversial statement, saying a pandemic could claim as many as 150,000,000 dead when his agency was only predicting 2 to 7 million. Nabarro's figure would have tracked the mortality of the 1918 flu after accounting for the tripling in world population that has occurred since then. Nevertheless, WHO gradually "dialed back" the prediction, at least to the point of saying that in truth no one could predict how many deaths might occur. Which in fact is the truth. They should have said that originally. Their 2 to 7 million low ball number was an absurd estimate based on the very mild 1968 pandemic deaths in the US.

Now Nabarro is in the news again, this time saying we are only two mutations away from a bird flu pandemic. Once again WHO has to "dial back" the sudden anxiety this prediction caused. An unsigned story in Canadian Press looks at some of the background to the latest foot-in-mouth episode.

"There's no way of knowing," Michael Perdue, an avian influenza expert with the WHO's global influenza program, said from Geneva. "There's no way to make that prediction."

The statement will be an attempt to address recent widely reported comments made by the UN's flu czar, Dr. David Nabarro.

Nabarro, who is on secondment to the UN from the WHO, told a reporter from the Portuguese weekly newspaper Expresso that H5N1 is two mutations away from becoming easily transmissible person to person. The comment was widely repeated in news reports around the world.

Reached Monday at Munich Airport, Nabarro explained he was echoing a theory he'd heard from Dr. Ab Osterhaus, the head virologist at Erasmus University in Rotterdam and a central player in the community of scientists tracking this virus. (Canadian Press)

Osterhaus, however, didn't admit to saying it, only that it was his gut feeling that "a couple" of mutations might be all that is necessary to turn this avian virus into a full-fledged human pandemic monster. But it was still just a guess, albeit an educated one.

But not the only one:

His comments underscore the fact that despite decades of study, scientists are not clear what changes an avian influenza virus needs to undergo to fully adapt to humans.

"The science is not there yet," said Adolfo Garcia-Sastre, a microbiologist who researches flu at Mt. Sinai School of Medicine in New York.

[snip]

He wasn't willing to make an on-the-record prediction of how near or far H5N1 is from becoming a virus that easily infects people, though he privately named a figure that is significantly higher than Osterhaus's guess.

So there you have it. Either it's a couple or a lot more. Or maybe it's already occurred. Or it takes only one.

Since we don't understand the biology of virulence and transmissibility well enough to make predictions, I think it's fair to say your guess is as good as mine. Well, maybe not quite as good. But I'm not telling you what my guess is.

Until later.