The U.S. Centers for Disease Control and Prevention is urging health care workers to accelerate bird flu testing for patients hospitalized with flu symptoms.

Two cases of bird flu have been detected at the Metro Richmond Zoo in Virginia, marking the first time the highly contagious virus has been found at the facility in its 30-year history. The cases come on the heels of at least three other recent outbreaks in the Washington region that have already killed an estimated 1 million chickens and put officials on alert.