The U.S. government yesterday reduced its forecasts for poultry exports by nearly 6 percent from last month partly because of an accelerating outbreak of avian influenza that has triggered wider-than-expected trade restrictions.

USDA, in a monthly supply and demand report, dropped its estimate for turkey exports in 2015 to 720 million pounds (327,000 tons) from 765 million pounds in March and 804 million last year. Exports for broiler chickens were pegged at 6.68 billion pounds, down from 7.1 billion last month and 7.3 billion last year.

The cuts came as USDA confirmed a second commercial flock of turkeys in South Dakota has been infected with the H5N2 flu. On Wednesday, the sixth commercial turkey flock of 31,000 birds in Minnesota was confirmed to be infected with avian influenza.  The latest inflected flock of 34,000 turkeys in South Dakota will be culled to prevent the spread of the disease, according to the USDA.

Turkeys in eight other states have tested positive for the same strain since the beginning of the year, prompting key overseas buyers such as Mexico and Canada to limit imports of U.S. poultry and eggs from states and counties with infections. The most damaging restrictions to the $5.7 billion U.S. export market have been countrywide import bans imposed by China and South Korea.

“We didn’t expect China or South Korea really to take as severe, drastic action as they did,” said Jim Sumner, president of the USA Poultry & Egg Export Council.

Last year, China and South Korea accounted for about $428.5 million in export sales of poultry meat and products, according to USDA data. Strength in the U.S. dollar, which makes U.S. farm products less attractive to overseas buyers, makes it difficult for exporters to expand business in the face of trade restrictions due to bird flu, the USDA said.

The number of U.S. infections in poultry has been climbing as migratory ducks, which are believed to be spreading the virus, are traveling to northern states after spending the winter farther south, experts said.