One more case of measles has been confirmed in Auckland today, bringing the total number of people sick with the disease to 40.
The new case adds to the total from Westlake Boys High School, which now has 20 ill students.
More than 750 people have been deemed at immediate risk of catching the highly contagious disease from having direct contact with an infected person, the Auckland Regional Public Health Service (ARPHS) said today.
It also said it is expecting more cases to be confirmed, particularly from the North Shore school.
"ARPHS has been working closely with the school principal and staff. The school has distributed ARPHS' information letters about measles to students, their parents/caregivers, staff and the board of trustees," it said in a statement.
The majority of the confirmed cases in Auckland are people who have recently been overseas, or have been in contact with someone who has travelled.
"However we are now starting to see an increase in the people who are not connected with travel, which means that measles is spreading in the community," ARPHS said.
A warning was posted on the school's website today, telling non-vaccinated pupils to stay away until at least March 8.
However, the school said it had no new comment to make today, and directed all media enquiries to the ARPHS.
The ARPHS is contacting all people who may have been in contact with an infected person, estimated at more than 750 so far.
They are being told to remain at home if they have not been vaccinated themselves.
Health professionals are also being warned to stay vigilant, and look out for signs of measles in patients.
"Measles is a very serious disease that causes fever, cough, sore eyes and a rash. There is no treatment, and complications can be severe, including hospitalisation. The only way to prevent measles is to be vaccinated with two doses of the MMR vaccine," said Dr Richard Hoskins, the medical officer of health managing the situation.
"Measles is highly infectious, with one person able to spread the disease to an average of 13 unimmunised people - just being in the same room as someone with measles can be enough to catch it."