Department of Agriculture Undersecretary Ted McKinney has spoken out about the African swine fever outbreaks in Vietnam, explaining that the current death toll is estimated to be 20 percent of the national herd.

There were some reports that the number might be higher, said McKinney, who spoke to reporters on a conference call from Ho Chi Minh City, Vietnam, during a government and agricultural industry trade mission.

Vietnam government officials said this week the spread of the disease has shown signs of slowing and are urging farmers to restore pig herds battered by the outbreak.

"It's tough to say whether African swine fever is contained," said McKinney, who has met with overseas buyers as well as Vietnamese government officials during the trip.

Still, McKinney pointed to one positive sign: the chief executive of a large Vietnamese feed company told him the spread of ASF does not seem to have accelerated in the country.

US pork exports have jumped and hog processors have been vying for business in China, the world's biggest pork consumer, and other markets in Asia, where African swine fever has devastated hog herds, pushed pork prices to record highs and sent imports rocketing. Though not harmful to humans, the disease is deadly to pigs, with no vaccine available.

USDA pork export sales data issued on Friday for the period from 4 to 10 October included "a significant quantity" of sales that may have occurred in previous weeks - including exports to Mexico jumping to a weekly record of 132,381 tonnes, from 2,692 tonnes a week earlier.

In addition to pork, Vietnamese buyers also are purchasing poultry, beef and water buffalo as part of the country's preparation for the Lunar New Year celebrations in January, McKinney said.

"African swine fever continues to clearly be a problem, not just for the countries that have it, but countries like our own that don't want to get it," said McKinney, the USDA undersecretary for trade and foreign agricultural affairs.

The delegation took special precautions ahead of the trip to Vietnam - including no visits to Vietnamese farms - to help ensure that members did not accidentally bring ASF back with them to the United States, McKinney said.