Passengers who were at Sydney Airport on February 3 are being urged to keep an eye out for measles symptoms after potentially contracting the disease from an infectious traveller.

The ill passenger was on Qatar Airways flight QR906 from Doha to Sydney, which departed Doha on February 2 and arrived at Sydney International Airport at 6.25am on February 3.

Passengers who were at Sydney Airport on February 3 are being urged to be alert for measles symptoms. Shutterstock

The passenger was then in the international transit lounge until approximately 9am before taking flight QR906 to Canberra.

Passengers on the flight or who were in the airport's international transit lounge at the same time are advised to watch for signs and symptoms of measles until February 21.

The passenger became unwell prior to leaving Pakistan.

The sites do not pose any ongoing risk to the public. The time from exposure to the onset of symptoms is from a week to 18 days.

“If you develop symptoms please call ahead to your GP so you do not wait in the waiting room with other patients,” Director Communicable Diseases Branch Director Dr Vicky Sheppeard said.

“The measles-mumps-rubella vaccine is safe and effective protection against measles.

"It is free for anyone in NSW born during or after 1966 who hasn’t already had two doses.

"If you’re unsure whether you’ve had two doses, it’s quite safe to have another.”

Measles is highly contagious and is spread in the air through coughing or sneezing by someone who is unwell with the disease.

Symptoms include fever, sore eyes and a cough followed three or four days later by a red, blotchy rash spreading from the head and neck to the rest of the body.

NSW Health has urged people travelling to South and South East Asia, where measles is prevalent, to ensure they are fully vaccinated before heading overseas.