The latest technology allowed scientists at the Colorado Department of Health and Environment to link a pair of illnesses in Denver to the same E. coli pathogen sickening several people in California.

The Colorado scientists used an international computer database called PulseNet, created by officials who track illnesses.

"We then saw 11 cases with the same DNA fingerprint in five states," said Jim Beebe, Colorado’s chief microbiologist.

"By using information shared worldwide, we can identify outbreaks that once were only viewed as isolated events," Beebe said.

Once Colorado made the link and the source was identified, the USDA announced on June 3 that United had issued a 75,000- pound recall of ground beef processed at its plant on April 20. It later expanded the recall to 5 million pounds of ground beef.