• They are under 12 months of age and not immunised,
• If they have a weakened immune system,
• Or if they are pregnant and know they are not immune.
And passengers who don't know if they're immune to measles or vaccinated should check with their doctor or call Healthline on 0800 611 116 for advice.
Medical Officer of Health at ARPH, Dr Maria Poynte, said people are most at risk if they've not been vaccinated or haven't had the disease previously.
Symptoms can take seven to 14 days to appear and include a high fever, runny nose, cough and sore red eyes.
A few days later a rash starts on the face and neck, then spreads to the rest of the body.
If you do start to develop symptoms that could be measles, also contact your doctor, Dr Poynte said.
And be sure to call ahead to prevent potentially infecting others in the waiting room.
Meanwhile, the state of emergency in Samoa, declared due to the measles epidemic, has been extended to December 29, 2019.
This is to administer vaccinations to the remaining population who have yet to be immunised.
This is an estimated 16,000 people among the population of approximately 190,000.
The measles epidemic has killed 72 people in the country since it began two months ago.