International-bound travellers under the age of 54 should be checking their measles vaccination history, a health official has warned amid another public alert for the highly contagious disease.

NSW Health on Saturday issued an alert for people in Sydney International Airport in the early hours of August 17 after an unvaccinated man on a flight from the Middle East was diagnosed with measles.

The alert extends to those on the same Etihad Airways flight EY 451 that landed at 11.55pm on August 16 and those at customs, baggage carousels and the arrivals area in the hours afterwards.

“Anyone who develops symptoms of measles should phone their GP to ensure they don’t wait alongside other patients before seeing their doctor,” communicable diseases director Vicky Sheppeard said in a statement.

A similar alert was issued on Friday after two people returned home with the disease from South America and New Zealand, and travelled through Sydney CBD and Hazelbrook from August 15 to 19 while infectious.

Dr Sheppeard said the three cases demonstrated the importance of people born after 1965 checking their vaccination history before travelling overseas.

“Measles cases worldwide have dramatically increased in 2019, and many countries are experiencing large and ongoing outbreaks,” she said.

“This means that all travellers are at risk of measles if they are unvaccinated, not just those travelling to the usual hotspots.”

Two doses of the measles-mumps-rubella vaccine provide lifelong protection in 99 per cent of those vaccinated.

Anyone born after 1965 who haven’t had two doses can access it for free in NSW, ACT, Victoria, Western Australia and Queensland.

It’s also free nationwide for all people born after 1998 or refugees of any age.

Dr Sheppeard sought to reassure those unsure about their dose history that having another dose is safe.

All overseas travellers are recommended to seek medical advice at least two weeks before departure about what vaccinations they may require.

– AAP