VANCOUVER, April 29 (Xinhua) -- A measles disease outbreak was declared in central Alberta and the western Canadian province's major cities such as Calgary and Edmonton.

There have been 22 cases of measles in the province during recent weeks, and more are expected as the disease has a long incubation period, according to Marcia Johnson, medical officer of health for the Edmonton Zone.

The declaration also meant changes to the recommendations for routine immunization for children, she added.

"It allows us to offer measles vaccine early to help protect infants over the age of six months to just under 12 months. Those infants usually are not eligible for measles vaccine and therefore are not protected against the disease," she said.

There was a breakout of measles among children in neighboring British Columbia weeks ago but the disease was under control later.