A measles outbreak that began at Disneyland in December and affected some communities in Arizona is waning.

California health officials said the outbreak will be considered over in the state on Friday if there aren't new cases.

The outbreak began when 40 people became exposed to measles while visiting Disney theme parks in Southern California. They then spread the virus to 30 family members.

A measles outbreak is considered over when 42 days — or two incubation periods — have passed since the last onset of the rash.

The highly contagious disease was declared eliminated from the United States, but travelers can still bring in the virus from abroad.