Pandemic: from the Greek, pan- (all) + -demos (the people)
Pandemic (according to the WHO): from external pressure and internal weakness, highly-virulent + "justified" panic + all + the people
The definition of a pandemic used to be simple: a worldwide outbreak of disease in excess of what would normally be expected (a global epidemic).
The WHO even came out with a definition of worldwide spread (community transmission in 2 or more WHO regions).
But now, apparently, the WHO intends to change the definition of a pandemic from simple to stupid.
Bowing to pressure from member nations, the WHO is (according to the New York Times) going to change the definition to include the severity of disease, and will probably do so in such a way that the current H1N1 outbreak will never count as a pandemic (unless it becomes more virulent, which it very well might).
Now, you may remember that we've had three pandemics in the last century, one in 1918, one in 1957 and one in 1968... or, at least, that used to be true. If this new definition goes into effect as described, we'll have to erase those last two from the list, because they were no more severe than this new H1N1 strain appears to be right now.
Whether a given outbreak is a pandemic or not is a separate question from how severe that pandemic is.
If the WHO thinks a severity scale would be useful, then by all means they should create one. There are some good arguments against using a severity scale (flu viruses evolve so quickly, severity varies between and within countries, etc.), but it's possible a severity scale would help countries and communities to better plan for and respond to a pandemic... but the role of a severity scale should be to better describe an existing pandemic, not to determine whether an outbreak is a pandemic.
If the WHO goes through with this, there will be two definitions of a pandemic: One used by epidemiologists and other public health professionals, and one used by the WHO --because the WHO's new idea for a definition doesn't make any rational sense. By setting up such a situation, the WHO will be undercutting its own credibility in a time when its ability to lead is more important than ever.
Instead of caving to the pressure of politicians from the member nations who feel that declaring a pandemic would cause "unjustified panic," the WHO should be using this as a teachable moment, to educate the public about what a pandemic is, what can be done about it, and why panic is never a justified reaction regardless of severity.