WHO calls emergency meeting on swine flu

* WHO convening emergency committee to advise on swine flu

* 12 of 18 virus samples in Mexico same as California cases

* More epidemiological info needed for pandemic alert change

GENEVA (Reuters) - The World Health Organization said on Friday it was calling an emergency committee to advise whether outbreaks of swine flu in humans in the United States and Mexico constituted an international public health threat.

A deadly strain of swine flu never seen before has broken out in Mexico, killing as many as 60 people and raising fears of a possible spread across North America.

"WHO will convene, sometime in the very near future, an emergency committee under the International Health Regulations, which will consider whether or not this event constitutes a public health event of international concern," WHO spokesman Gregory Hartl told Reuters in Geneva.

Hartl also said that 12 of 18 samples taken from victims in Mexico showed the virus had a genetic structure identical to that of a swine flu virus found in California.

But more epidemiological information was needed before any change to the WHO's pandemic alert level, currently at '3' on a scale of 1 to 6, he said.

"The technical people in our Organization are saying that before we know how pandemic a virus can be, we need to know how efficiently it is transmitting and how widespread it is," Hartl said.

(Reporting by Stephanie Nebehay; Editing by Kevin Liffey)