Infection control workers at UPMC Presbyterian hospital in Pittsburgh, Pa., found Legionella bacteria in sinks in three patient rooms, but officials said no patients have tested positive for Legionnaires' disease, according to an article on the TribLive website.

Legionella occur naturally in the environment, and health experts have said Western Pennsylvania's combination of abundant water and old plumbing can help the bacteria to flourish.

“Regardless of the disinfection technology, because a water distribution system is complex and the water doesn't evenly flow through the system, you may have positivity despite having disinfection,” Janet Stout, a microbiologist and director of the Special Pathogens Laboratory, Uptown, said in the article.

UPMC officials said they are intentionally aggressive about monitoring Legionella since discovering the bacteria in ice machines at Presby two months ago. The bacteria, uncovered in May, contributed to one patient's death and sickened two others, hospital officials said.

Read the article.