Berry said investigators were not surprised by the number of positive skin tests because so many of the employees are foreign-born. People born in other countries are nearly nine times more likely to have TB than those born in the U.S., according to the U.S. Centers for Disease Control and Prevention.
"We suspect many may have been infected in their home countries before they came to the U.S.," he said.
There is no danger of spreading the disease through the chickens, Berry said.
Officials at House of Raeford in North Carolina, which owns the Rutherford Road plant, could not be reached for comment.
There were about 14,000 cases of active TB recorded nationwide in 2005, CDC reports. And there are about 300 new cases a year in South Carolina, Berry said. One was confirmed at Clemson University on Sunday. None of those cases is related to the drug-resistant strain identified in an Atlanta lawyer last month.
Berry said TB investigations are common in South Carolina.
"When a physician or hospital makes a diagnosis of TB, it's reported to us," Berry said. "And when we get that report, we begin a close-contact investigation."
Though some 900 people work at the plant, only 286 were tested, based on a CDC formula that determines the closest contacts, he said. But others will be tested if necessary, he said, and investigators will return to the plant in about eight weeks to retest the workers to make sure none has become active in the interim.