The Mexican government declared a national animal health emergency on Monday in the face of an aggressive bird flu epidemic that has infected nearly 1.7 million poultry.

More than half the infected birds have died or been culled, the agriculture ministry said of an epidemic that was confirmed on Friday by the UN's Food and Agriculture Organization (FAO).

"We have activated a national animal health emergency... with the goal of diagnosing, preventing, controlling and eradicating the Type A, sub-type H7N3 bird flu virus," the ministry said.

Health officials keep a close watch on such outbreaks in Mexico since so-called swine flu began there in 2009. The H1N1 virus spread into a global pandemic that claimed the lives of 17,000 people.

The virus responsible for Mexico's current bird flu outbreak, H7N3, has occasionally caused human disease in various parts of the world, according to the UN, but has not shown itself to be easily transmittable between humans.

The outbreak was first detected on June 20. The FAO reported on Friday that 1.7 million birds had been contaminated and 870,000 had died at 10 breeding farms in the western state of Jalisco.

The emergency declaration on Monday included provisions for quarantine, slaughter, vaccination, and the destruction of infected products.

The agriculture ministry said poultry farming "contributes up to 40 percent of the total volume" of the country's livestock production, and the "economic loss" from this epidemic "is and will be irreparable."