Clinical director Dr Julia Peters said the service had been working with the North Shore school for just over a week when the first case of measles was found there.
"This is definitely more than what we'd normally see. We're working hard to contain the measles within the Auckland region."
Dr Peters said many people who had come down with the disease had recently been overseas and, in particular, in the Philippines.
She said it had not yet reached a point that may see a mass measles outbreak like in 2011, when nearly 500 cases were reported.
The public health service has sent materials to parents and students at Westlake Boys High and asked that those students unsure of their immunisation status against measles to stay away.
"What we're trying to do is isolate those students as well as those who have measles, because students who are not immunised can get sick," she said.
Another seven cases of measles in Auckland are being investigated - three of them from the same school.
Headmaster David Ferguson said the school had sent out several newsletters and public health material to parents and held assemblies to inform pupils of the situation.
"We had nine confirmed cases as of Friday and that number has now risen. We don't know any connection between them other than that they come to the same school," Mr Ferguson said.
A pupil who was among the first to be confirmed with the disease and is understood to have been hospitalised as a result was yesterday on his way to making a speedy recovery, Mr Ferguson said.
Pupils affected range from Year 9 to Year 13 - aged 13 to 18 - and there is a possibility that some pupils will be asked to stay away longer than two weeks.
"We just want to make sure that our students are safe and well and back at school as soon as possible."
What to watch for Symptoms
* High fever.
* Respiratory symptoms such as runny nose, cough, red eyes.
* Small white spots inside mouth.
* Red, blotchy rash on face and neck and later over entire body.
Advice
* Ensure you or your child has had the two doses of the measles vaccine. Immunisation is free for children and adults born after 1969.
* If you suspect you or your child has measles, call your GP before going to a medical clinic as the disease is highly contagious and spreads through the air.
