More than 1000 people were exposed to measles at a school holiday camp in Rotorua.
Adults and children as young as four who attended the Seventh Day Adventist camp in Rotorua may need to go into quarantine after an Auckland child with measles attended.
Auckland Regional Public Health Service is working to alert 1200 camp-goers that they may be at risk of the illness after being exposed to the virus at the Tui Ridge Park camp.
The children at the camp were aged four to 15 years.
Auckland Regional Public Health Service clinical director Dr Julia Peters said the child was infectious on October 5 and 6.
Public health units across the North Island have received the contact details of the attendees in their regions, so units could advise people at the camp about their risk and what action to take.
"If camp-goers are not immune they will need to stay home in quarantine from today until the end of October 20," Dr Peters said.
She said while people might not show any signs of measles yet, people could spread the virus five days before they developed a rash.
About 1000 of the attendees from the camp were from Auckland, with the rest from Tauranga, Rotorua, Hamilton, Lower Hutt, Wellington and Manawatu.
Seventh-Day Adventist Church general secretary Hugh Heenan said Tui Ridge remained fully operational.
"One staff member was briefly there but was not fully immunised so is staying home as a precautionary measure."
He said thankfully their own preventive measures had made it easy - such as an understanding of who was or wasn't immunised and the support from the DHB had been wonderful.
Toi Te Ora medical officer of health Phil Shoemack said they were contacting people in the Bay of Plenty who had attended the camp to see if they were immunised.
"If they are not immunised we require them to be in quarantine for another week."
Shoemack said this simply added to the Toi Te Ora workload.
"We've been busy dealing with measles since July. We've followed up well over 1000 people in that time. This adds to our workload.
"It's another reminder of the value and importance of being vaccinated because anyone who is vaccinated isn't at risk."
Tui Ridge was unable to comment at this time.
Anyone who was at the camp should be vigilant for symptoms of the highly infectious disease and should call their doctor or Healthline.