PORTLAND, Maine (AP) Maine health officials say they’re aware of cases of chickenpox at a Portland facility being used to house asylum seekers, and they’re working to contain the viral disease.

The Maine Center for Disease Control and Prevention says in a statement Saturday that individuals staying at Portland Expo are considered exposed to the disease.

Maine CDC said later in the day there are a “limited number” of chickenpox cases.

Portland Expo’s a basketball arena that’s currently being used to house asylum seekers while they seek permanent housing. They face an Aug. 15 deadline to leave the facility.

Portland city officials say they’re working with Maine CDC to limit exposure. The city’s informing volunteers who visited the Expo on July 26 or later to watch for symptoms and check vaccination records.

The disease’s best prevented with a vaccine.