The World Health Organization says there are now 40 confirmed cases of swine flu in the United States and that it "very concerned" about the disease's spread.

WHO says none of the cases in the U.S. have been fatal.

But the U.N. agency says it could decide in a matter of hours whether to raise its pandemic alert level as a result of the increasing number of confirmed swine flu cases in Mexico and elsewhere.

Spain confirmed the first swine flu case outside North America on Monday.

WHO spokesman Paul Garwood said other issues will also be discussed at the Monday emergency meeting chaired by the agency's chief Dr. Margaret Chan.

He said in the Spanish case the disease was transmitted in Mexico and not passed among people in Spain.