Vietnam says the bird flu virus has been found in poultry in the southern Mekong Delta for the second time this month.
The Department of Animal Health said Saturday the H5N1 virus was detected in at least one duck in Ben Tre province.
Earlier this month, the bird flu virus was detected in ducks and geese in the same province.
Forty-two people have died of bird flu in Vietnam, which has the second highest number of human fatalities from the H5N1 strain of the virus after Indonesia.
However, Vietnam has not reported any cases of bird flu in humans this year, and health authorities have praised the country for its efforts to combat the virus since it surfaced there in 2003.
Medical experts are concerned the virus may change into a form that is easily spread from human to human.
Some information for this report provided by AFP and AP.