HONG KONG, March 12  -- A new variant H7N6 virus was found in chickens in Chinese mainland markets in a H7N9 flu virus study conducted by the University of Hong Kong which made the results public on Thursday.

Researchers from the university joined hands with mainland institutions to monitor the evolution and spread of H7N9 virus over 15 cities across five provinces in China.

The researchers found that H7N9 viruses have diverged into three geographically distinct clades in east and south China, and a previously unrecognized H7N6 variant emerged in chickens in live poultry markets in Jiangxi province, when chickens in live poultry markets are the direct source of H7N9 human infections.

However, overt antigenic changes have not been identified, thus the candidate vaccine strains recommended by the World Health Organization in 2013 will still be effective.

The expansion of its genetic diversity and geographical spread indicates that, unless effective control measures are in place, the H7N9 virus is likely to persist and spread beyond the region, researchers warned.

It is suggested that central slaughtering and closure of live poultry markets are key measures to prevent avian-human transmission.

To date, a total 638 laboratory-confirmed cases of human infection with H7N9 virus have been reported globally since 2013, with 229 deaths recorded as of March 10, according to the university.

This study was published in international scientific journal Nature on Thursday.