The virus currently circulating in Mexico and the United States and which has killed at least 20 people is not swine flu, the Paris-based World Organization for Animal Health (OIE) said Monday.

"The virus has not been isolated in animals to date. Therefore, it is not justified to name this disease swine flu," the OIE said in a press statement, dpa reported.

The virus "includes in its characteristics swine, avian and human virus components," the OIE said, and urged that it be called "North American influenza," after its geographic origin.

The OIE said it was "urgent" that scientific research be carried out to determine the susceptibility of animals to what it said was a "new virus."

If animals were susceptible, "virus circulation could worsen the regional and global situation for public health," the organization said.