"This is the largest outbreak of mumps in more than 20 years," [Julie Gerberding] told a news briefing yesterday. "More than 1,000 cases are under investigation."

The alert says the health department "has been following a large outbreak of mumps that originated in Iowa," which has the potential to spread further. It asks health care providers to enhance surveillance for mumps and to promptly report any suspected cases.

AP PHOTO - Tina Rolfes gets a mumps, measles, and rubella immunization in Dubuque, Iowa, where the mumps outbreak is at its worst, affecting adults aged 18 to 22, most on college campuses.