A measles warning has been issued by WA's health department following two confirmed diagnoses in adults holidaying overseas.
The alert covers areas around Bentley and Royal Perth Hospitals and Perth Airport.
The two adults were infected separately while overseas, with one in Bali and another in one of thee Southeast Asian countries.
These cases may have been infectious to others at Perth international airport, a GP surgery, Royal Perth Hospital and Bentley Hospital B Block. See below for a detailed timeline.
Health authorities have been trying to get in touch with potentially exposed individuals.
"Measles is contagious for about four days before and after the development of the rash. Children and adults who have been unwittingly exposed are at risk of developing measles if they are not immune," WA Health Medical Epidemiologist Dr Gary Dowse said.
"A person is considered immune to measles if they have previously received two doses of a measles vaccine or were born before 1966.
"Anyone who thinks they are infected should call ahead and mention their possible contact with measles so they can be isolated when they arrive at the GP surgery or Emergency Department, to prevent infecting other patients and staff."