Health officials are alerting residents of Pierce County and south King County of a measles outbreak.
The disease has been confirmed among eight members of an extended family in south King County and in an infant who was infected in the emergency department at Mary Bridge Children's Hospital in Tacoma.
The News Tribune reports investigators believe the infant was exposed when members of the infected family went in for treatment.
County health departments say the outbreak is linked to a person who returned to the United States from the Pacific Islands on May 26 with the measles.
Seattle-King County Public Health is working with a community from Micronesia connected to the outbreak.
Before this outbreak, 15 cases of measles had been confirmed in Washington this year.