When an outbreak hits, like the current one involving salmonella and a 550 million shell egg recall in the U.S., everyone wants the source to be found immediately. But government food-safety experts say it's not that easy. "The mantra is: You have to be fast and right," said Ian Williams, chief of the Centers for Disease Control and Prevention (CDC)'s outbreak response branch. "You can never be fast enough and you always have to be right."

Sometimes mistakes are made: in 2008 the tomato industry took a major financial fall when the Food and Drug Administration (FDA) and CDC identified tomatoes as the culprits in a salmonella outbreak. Later, hot peppers were discovered to be the real source. In the case of Wright County Egg, the company that originated the current egg recall, it took 10 days after two states identified the company as the common egg supplier in illnesses for the FDA to inform Wright. While the evidence was gathered in the last week of July, it wasn't until Aug. 13 that a recall was announced.  


Deciding when there's enough evidence to alert a company or the public of an outbreak is a judgment call, said Jeff Farrar, the FDA's associate commissioner for food protection. "This is where hindsight and second-guessing come in," he said. "We try to do the best we can."