HO CHI MINH CITY - The H5N1 strain of avian influenza virus, clade 2.3.2.1C, which has been prevalent in Vietnam's northern regions, was discovered for the first time in a number of dead ducks in southern Dong Nai province, about 1,120 km from capital Hanoi, local media reported Friday.

State-run Vietnam News Agency quoted an official from Dong Nai province's Animal Health Department as reporting that results were confirmed after a sample from the birds tested positive for the virus.

Previously, the A/H5N1 strain, clade 1.1, were found in affected poultry sold at many markets across Vietnam, with the availability rate up to 6 percent in 2013.

From late 2013 and particularly in the first two months of 2014, the A/H5N1 strain, clade 2.3.2.1C, has penetrated into southern regions, along with clade 1.1. To date, eight out of 13 city and provinces in southern Mekong delta were reported to be struck with avian flu outbreaks.

Dong Nai province is home to the largest number of poultry raised nationwide, with over 12 million. It is also located at the gateway of Ho Chi Minh City, the key economic hub in the south. As such, the transportation of poultry products is more likely to trigger the outbreak of bird flu, according to the local animal health department.

Currently, only 10 percent of the poultry in Dong Nai has been vaccinated against the A/H5N1 strain of the virus. Earlier, the province detected two bird flu cases in Trang Bom and Cam My districts.