A vaccinologist is calling for calm as a passenger arrives in New Zealand carrying measles.
Passengers flying from Los Angeles to Auckland a week ago may have come into contact with the infection.
But vaccine specialist Helen Petousis-Harris from the University of Auckland says the outbreak is already out of control, and that person with the highly infectious disease is unlikely to be the only one bringing it in.
"There's so much measles globally at the moment it's probably happening on a daily basis, and it's going to continue to happen."
The number of confirmed cases in Auckland has risen to 616. The disease was officially eradicated in New Zealand two years ago, meaning the only cases are the result of people bringing it in.
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Symptoms include a fever, runny nose, cough, sore red eyes and then a rash.
"There is some risk that other passengers may contract measles if they are not immune," Medical Officer of Health Dr Craig Thornley said on Friday.
"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."
Those who fear they've been infected advised to get a booster shot.
"It's not worth doing a test," says Dr Petousis-Harris. " It's just easier to go and get a dose of vaccine."
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But don't just go to your GP - call Healthline or ring them ahead of time.
"If you feel unwell, please don't just turn up. It is important to call first, because measles is highly infectious and you could infect others in the waiting room," said Maria Poynter of the Auckland Regional Public Health Service.
The World Health Organization (WHO) recently named the anti-vaccination movement as one of the top 10 threats to global health.
More than 100,000 people died of measles in 2017, the WHO says, most of them pre-school children. Before a vaccine was available, millions used to die annually.