Passengers on the same flight as a baby with measles are being tracked the length of the country as health authorities try to halt the march of the highly contagious disease.
Public health authorities said they had contacted most of the 266 passengers who arrived at Auckland International Airport last weekend on a Singapore Airlines flight when parents of the sick 7-month-old sought medical attention after arriving in the country.
Auckland Regional Public Health spokesman Dr Richard Hoskins said nurses were contacting all passengers to assess whether they were susceptible to catching the disease.
Previously, the country's 16 measles cases had been linked to an international hip-hop event held in Sydney last December. Most patients were from two extended family groups from the Turangi dance troupe Original Kids Krew.
Now health authorities from nine regions - including the South Island - are on a nationwide alert after passengers have dispersed throughout New Zealand.