Updated

The Centers for Disease Control and Prevention (CDC) has called 30 employees back to work who had been furloughed during the partial government shutdown, in order to help stop the spread of a salmonella outbreak which has sickened nearly 300 people in 18 states, MedPage Today reported.

This move came around the same time the CDC announced that some of the salmonella strains associated with the outbreak have been found to be resistant to one or more antibiotics.  And according to health officials, 42 percent of those who have contracted the disease have been hospitalized.

"That's a high percentage," Barbara Reynolds, a CDC spokeswoman told USA Today. "You would expect about 20 percent hospitalizations with salmonella Heidelberg."

Like many other government agencies, the CDC has been operating on a minimal staff. Employees deemed “non-essential” have not worked or received paychecks since the partial government shutdown began.

But according to an email to MedPage Today, “about 30 people working on foodborne analysis and outbreak response [were brought back to work].”

The source of the outbreak has been traced back to raw chicken products produced by three Foster Farms facilities in California, according to a statement from the U.S. Department of Agriculture (USDA).

The outbreak appears to have begun in March and the USDA was notified of the illnesses in July, said Dan Engeljohn of the USDA's Food Safety and Inspection Service. Investigators had a difficult time pinpointing the source of the illnesses, Englejohn said.

A spokesman for Foster Farms says no recall was in effect and that the infections were caused by eating chicken that was undercooked or improperly handled.

The USDA has not directly linked the outbreak of illnesses to a specific product or production period. The USDA mark on suspect packages would read: P6137, P6137A and P7632.

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The Associated Press contributed to this report.