The recent arrival of an international air passenger diagnosed with the highly infectious English measles has sparked a warning from Auckland health authorities.

The passenger arrived in Auckland aboard Qantas flight QF043 from Sydney on October 31.

While immunisation had made measles infection rare in Auckland, there was a concern that it could spread rapidly in unimmunised groups, Auckland regional Medical Officer of Health Dr Sheryl Jury said.

Auckland Regional Public Health Service advised any travellers on the flight, or their family members, to seek advice from a doctor if they had measle-like symptoms, and to avoid young children.

It was important to alert doctors about the possibility of measles before visiting, to allow them to make arrangements to avoid infecting others, Jury said.

Typical measles symptoms were fever, a runny nose and sore eyes, followed by a red blotchy rash starting on the face before spreading to the body.

People were infectious for five days before developing the rash. It usually took eight to 12 days to develop symptoms after being exposed.

Almost all cases made a complete recovery.

However, up to a third of children developed complications such as middle ear infection and diarrhoea, Jury said.

The highly infectious illness could also sometimes have serious consequences such as pneumonia and encephalitis (inflammation of the brain).

New Zealand children are immunised against English measles at 15 months and four years of age.

English measles (morbilli) is caused by a different virus to german measles (rubella).