Bird Flu's Sweep Worries Health Officials, By ALEXANDER G. HIGGINS Associated Press Writer © 2006 The Associated Press

GENEVA — For years after its appearance in 1997 in Hong Kong, the current bird flu virus seemed corralled in a few east Asian countries. But in the past four months, it has spread across Europe and into Africa, bringing to 31 the number of countries with sick birds.

People have caught it in a quarter of those, and just six people outside east Asia have died. The virus is still not easily caught by humans.

Even so, its sudden sweep across continents on the wings of birds has stunned public health officials. And most say they cannot predict where or when this disturbing germ might mutate into a form that could unleash a deadly flu epidemic.

"Anywhere the virus lands," said Dr. Mike Perdue of the global influenza program for the World Health Organization.

For many months, most experts said Asia was the most likely starting point because of its large population and ubiquitous animal markets. And many still believe that. But it's all speculation.