Seventeen people have been confirmed to have contracted measles in what is the second large outbreak in Auckland this year.
The Auckland Regional Public Health Service has confirmed the outbreak, which has left three people hospitalised.
All cases are linked to Oratia Primary School and almost all those with the disease were unimmunised.
Though the outbreak has not spread further, the number of cases shows how highly contagious the disease is, according to ARPHS.
Medical Officer of Health Dr Richard Hoskins said ARPHS is taking appropriate steps to trace people who may have been exposed through interaction with the cases while they were infectious.
He says that may involve exclusions at some schools and early childhood centres.
More than 200 individuals, as well as large groups such as schools, have been traced so far.
"Measles must be taken very seriously, especially as we are seeing an increase in the number of cases presenting," Dr Hoskins said.
"It is a disease that can have severe complications, especially in vulnerable groups in the community, including children too young to be immunised, pregnant women, and those with suppressed immunity."
Dr Hoskins said people with the disease need to kept at home, away from school, work, social activities, sports and public places.
"Getting measles can be avoided by immunisation with the MMR (measles, mumps, rubella) vaccine, which is typically given in two doses, at 15 months and 4 years of age," Dr Hoskins said.
"Immunisation not only protects your child from serious illness, but also protects more vulnerable children and members of the community who could suffer more serious illness or death."By Paul Harper @Snappy_nz Email Paul