Seventeen people have been confirmed as having measles in Auckland, the second large outbreak in the city this year.
Auckland Regional Public Health Service (ARPHS) medical officer of health Richard Hoskins said all cases were linked to Oratia Primary School in west Auckland, with three people requiring hospitalisation.
Almost all of those struck by the illness were not immunised.
Dr Hoskins said ARPHS was trying to trace people who may have been exposed to the infection. More than 200 individuals, as well as large groups such as schools, had been traced so far, with some instructed to isolate themselves.
"Measles must be taken very seriously, especially as we are seeing an increase in the number of cases presenting.
"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 urged those who had been isolated to remain at home and avoid contact with other people.
"And as always, we urge people to be vigilant if they suspect they could have measles, or have been exposed to someone who could have measles.
"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.
"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."
Should fluoride in water be the responsibility of central government?