There's been an epizootic of unprecedented virulence, persistence and
spread in domestic poultry since 2003.  Despite extremely strenuous
efforts to contain the epizootic by destroying hundreds of millions
of birds, the epizootic has persisted, recurred, and spread over most of
eastern Asia and is now present in Europe.  Previous outbreaks of highly
lethal avian influenza in birds have always been contained and extirpated
before they spread outside an individual country or part of a country.

The longer the epizootic persists, and the larger number of people and
swine who are exposed to it, the higher the probability that a human
transmissible form will arise.  The WHO, the FAO and the governments of
the involved countries have been going flat out but so far have only
managed to slow and hinder the spread of this epizootic.  This applies
not only to poor countries, but technologically advanced ones like
Japan.  Since unlike previous outbreaks in Hong Kong, the Netherlands,
Pennsylvania, and elsewhere, control measures are not succeeding, and
the epizootic is continuing and worsening, it's a great deal more
likely that this particular strain is going to mutate into a human
pathogen capable of causing a pandemic than other strains were in the
past.

It was a real danger when an outbreak in Hong Kong killed about a dozen
people.  Killing every bird in Hong Kong stopped that epizootic,
eradicating the danger.  Perhaps a billion people have been exposed
to this strain, more all the time, and control measures are not succeeding.
So the present risk of a pandemic developing is much greater than at
any time since 1918.

Hysteria isn't very useful, but preparedness and surveillance are
necessary if a pandemic is to be mitigated, as well as continued
efforts to stop the spread of the epizootic.  While this epizootic
isn't sure to give rise to a pandemic, the risk is not only real, but
much higher than in the past many decades.

If you want actual numbers, and the details of the epizootic, the WHO
site (www.who.int) has lots.