More than 70 percent of random duck and geese samples have tested positive for bird flu (search) in Vietnam's southern Mekong Delta, but many farmers have refused to slaughter their flocks, officials said Wednesday.

"We still don't know how strong the virus is," said Nguyen Ba Thanh, director of the Can Tho regional animal health center. "It may kill or may not kill the poultry, but it shows that the virus is entrenched in the region."

Of more than 10,000 duck and geese samples gathered from poultry farms across 10 Mekong Delta (search) provinces, 71 percent have tested positive so far this year, Thanh said. The virus also was found in about 21 percent of sampled chickens, he said.

The test results suggest that more than 10 million out of nearly 20 million total birds should be slaughtered to try to stamp out the virus, he said. However, farmers are resisting local government orders to kill their flocks because of lost income.

The government has offered to pay 32 cents to 64 cents for each bird slaughtered. But birds sold on the market command $1.30 to $1.90 a piece.

Thanh said a meeting is scheduled next week to address the issue.

"We need stronger and unified measures from the government," he said.

Bird flu has also jumped to humans, killing 51 people in the region, including 36 in Vietnam, since the virus ravaged farms across the region in late 2003.

Experts fear that if the virus mutates into a form that could be passed easily from person to person it could spark a global pandemic and kill millions worldwide. However, there is no evidence that the virus has altered its form and most human cases have been traced back to contact with poultry.