The Centers for Disease Control and Prevention Tom Harkin Global Communications Center in Atlanta. (Image credit: James Gathany/Centers for Disease Control)

A sweeping salmonella outbreak has become so serious that the Centers for Disease Control and Prevention has called back 10 furloughed staff members to monitor this and other outbreaks.

Since March, almost 300 people have become sick in 18 states - mostly in California - and 42 percent have had to be hospitalized. That's a higher percentage of cases than what most salmonella outbreaks cause.

The CDC told ABC News that seven different strains of salmonella had been identified, and that some are resistant to drugs.

The salmonella was linked to raw chicken from three facilities of a California company called Foster Farms.

The US Department of Agriculture has not ordered a recall of the chicken.

The USDA has advised consumers to check all Foster Farms packages for these numbers: P6137, P6137A and P7632.

While salmonella is common, it can be deadly, particularly in young children, the elderly and people with weakened immune systems.

Tara Lounsbury said she'd served fried chicken to her family Monday night. After news of the outbreak, she checked the code number on the chicken package and found that it matched one of three package codes that the USDA ID'd as contaminated.

"Just wondering, what if my kids get sick?" Lounsbury said.

Foster Farms said it was taking additional steps to control salmonella and that its chicken was "safe if it's fully cooked and properly handled."

Since the government shutdown, now in its eighth day, only two of 80 CDC staffers usually assigned to food pathogens have not been furloughed.

The Associated Press contributed to this story.