MEXICO CITY — During the past three weeks, Mexican officials have culled 2.5 million birds at poultry farms in western Mexico in a strategy to contain an avian influenza H7N3 outbreak, AFP reports.

Almost 150 poultry farms have been visited by officials. Of these farms, avian influenza was discovered in 31 farms, 34 tested negative and results for the rest of the farms have not been issued yet. On June 20, the outbreak was first uncovered in Jalisco state. As a result, Mexico’s government issued a national animal health emergency on July 2.

One million vaccines have since been imported from Pakistan. Mexico’s farming officials claim they have developed a seed-based vaccine that will delivered to four laboratories in preparations to initially make more than 80 million doses.