Iowa's mumps epidemic continues to spread:
As of Thursday, the state has 605 suspected cases.
Health officials say while the highest concentration of cases is still in eastern Iowa, the mumps has shown up in at least one person in half of the state's 99 counties.
State epidemiologist Doctor Patricia Quinlisk calls it a "serious threat." She says officials are doing "everything we can" to get it under control.
Iowa Department of Health Director Mary Mincer Hansen says questions about how the epidemic started and why it hit Iowa haven't been answered.
As of Monday, six other Midwestern states had reported cases of the mumps -- Nebraska, Kansas, Illinois, Missouri, Wisconsin and Minnesota.