Health authorities say passengers on an Air New Zealand flight from Los Angeles last week may have been exposed to measles.

Photo: 123RF

Auckland Regional Public Health Service said an Auckland resident was infectious on flight NZ001 leaving LA at 9.40pm on Thursday 15 August and arriving early Saturday morning.

Specialist Dr Maria Poynter said there was "some risk" that other passengers could contract measles if they were not immune.

Passengers should check their medical records for vaccinations and watch for symptoms like fever, runny nose, cough and a rash.

People may be infectious for five days before a rash appears so may not know they have measles, the service said.

"There is some risk that other passengers may contract measles if they are not immune," Dr Poynter said.

"We would ask that anyone on this flight checks their medical records if they are under 50 years to see if they have had a least one MMR vaccination, or have had the measles previously, making them immune.

"They should also watch out for symptoms over the next few days - a fever, runny nose, cough, sore red eyes and then a rash," she said.

"Unfortunately people are infectious five days before the rash appears, so don't usually know they have measles. They continue to be contagious for five days after this."

Health authorities have also issued a warning to people on a flight between Wellington and Auckland last Saturday after an infectious passenger flew before they knew they had the measles.

The flight was Air New Zealand NZ416 that left Wellington at 9.45am.