Western Australians have been issued a measles alert, after an infected Singapore Airlines passenger disembarked in Perth on October 21.

The passenger was infected whilst on holiday in Japan, and was contagious for the duration of the flight.

The plane arrived at 5.15am on Friday October 21. Credit:Jay Cronan

Passengers who were travelling on Singapore Airline flights SQ 633 from Tokyo to Singapore and SQ 225 Singapore to Perth were potentially exposed to the disease.

The alert has also been issued for those who were in the arrival area of the Perth Airport International terminal at the time of the flight landing, and visitors to Forrestfield's Mead Medical Centre and St John of God Pathology on Friday October 21.