Yue Mai was last seen on Aug. 17, when she left her home in the 200 block of 28th Street to take an Alameda-Contra Costa Transit District bus to Oakland's Chinatown district, Thomason said.
Family members are especially concerned because Mai hasn't taken her medication for the disease, Thomason said.
Thomason said that at one point there were indications that Mai might be in San Francisco but nothing developed from those leads.
Mai is 5 feet tall and weighs 120 pounds, with brown eyes and gray hair. She was last seen wearing a light blue jacket and a jade bracelet on each wrist.
Anyone who locates Mai is asked to call the Oakland Police Department's missing persons unit at (510) 238-3641.