A gathering number of new influenza strains in the past five years has escalated the likelihood of a major influenza pandemic on the scale of the deadly Spanish flu, researchers say.

UNSW researchers in the school of public health are calling for better collaboration between countries and first responder agencies in the event of a flu pandemic.

Their study published in the Archives of Public Health identified 19 separate influenza strains that have emerged in humans during the past century, including seven in the past five years alone.

Raina MacIntyre, director of the UNSW's Integrated Systems for Epidemic Response, said the unprecedented rise in new strains appeared to be a true increase and not just a matter of more cases being detected.