CHICAGO (Reuters) - Georgia has confirmed its first-ever case of bird flu in commercial poultry, its agriculture department said on Monday, widening an outbreak of the disease into the United States’ biggest chicken meat-producing state.

A flock of 18,000 chickens used for breeding was culled after testing positive for H7 bird flu, according to the agriculture department. It said the birds in far northwestern Georgia were likely infected with a form of the virus that is not highly lethal because the flock did not show signs of illness.

The discovery came after officials in Alabama, Kentucky and Tennessee confirmed cases of highly pathogenic, or lethal, and low pathogenic H7N9 bird flu in breeding operations this month. U.S. officials have said the risk of the disease spreading to people from poultry or making food unsafe is low.

But the spread of highly pathogenic bird flu to poultry in new states would represent a financial risk for meat companies because it could kill more birds or require flocks to be culled. It could also trigger more import bans from other countries after South Korea and other buyers limited U.S. poultry shipments following highly pathogenic cases in Tennessee.

The worst-ever U.S. outbreak of highly pathogenic bird flu in poultry in 2014 and 2015 killed about 50 million birds, most of which were egg-laying hens in Iowa.

More than 200,000 breeding chickens in Georgia, Alabama, Tennessee and Kentucky have been killed in recent weeks by high and low pathogenic bird flu or culled to contain the virus, according to state officials. U.S. poultry producers had about 55.1 million breeder hens on hand as of March 1, according to the USDA.

In 2015, Georgia produced 7.9 billion pounds of chicken meat valued at $4.2 billion, the agency said.

“Poultry is the top sector of our number one industry, agriculture, and we are committed to protecting the livelihoods of the many farm families that are dependent on it,” Gary Black, Georgia’s agriculture commissioner, said in a statement.

Some companies are still feeling pressure related to the 2015 losses.

On Monday, Cal-Maine Foods, the biggest U.S. egg producer, said its quarterly sales fell about 32 percent from a year ago because prices were under pressure after farmers increased production in response to an outbreak two years ago.