Two people who were infected with measles in Bali have returned to Perth, sparking a warning hundreds of people could have been exposed to the virus on the flight or at various locations around the city.

The two were holidaying with their family at the popular tourist destination when they contracted the disease.

They were contagious when they travelled on Air Asia flight QZ 548 from Denpasar to Perth on December 20.

Passengers who were on the flight may be at risk of developing measles.

Others may also have been exposed if they were at the following locations at the weekend:

Saturday 20: Perth Airport international terminal arrival area, early afternoon Dan Murphy's bottle shop, Bull Creek; Pharmacy 777, and IGA supermarket in Willetton, 4:00pm to 5:00pm

Sunday 21: Olympic Medical Centre in South Street, Canning Vale, 9:00am to 9:30am Princess Margaret Hospital emergency department about 10am



WA's Communicable Disease Control medical coordinator Paul Effler said if anyone thought they were in those areas at the time and developed a fever with other symptoms including a cough, runny nose or sore red eyes within the next two weeks, they should stay at home and consult their doctor.

He said anyone with the symptoms should call ahead and mention their possible contact with measles so they could be isolated when they arrived at the GP surgery or emergency department.

'Record' number of cases diagnosed

There have now been three cases of measles being contracted by West Australians in Bali in the last few weeks, and there have been a record number of cases this year, with 43 West Australians having been diagnosed with the virus.

At least seven of those have been directly linked to Bali and one linked to Indonesia.

Dr Effler said measles was the most contagious disease known to humans.

"If you're susceptible or you're in the same area as someone as a measles case you will get it," he said.

Dr Effler said nobody was diagnosed with measles from exposure to the case in late November.

"The good news is most people in Western Australia are immune to measles," he said.

"Young children because they've been vaccinated and people born before 1966 because they actually got the disease as children."

The Health Department advises that measles is contagious for up to five days before a rash develops and four days after that.

While naturally occurring measles has been eliminated in WA for over a decade, occasional cases and small outbreaks occur with tourists or residents returning from overseas.