The MidCentral District Health Board has issued a caution to those who attended the regional Tainui Waka Kapa Haka Festival held on Saturday April 16 at the Claudelands Event Centre in Hamilton.
About 5000 people attended the event and authorities say they may have been exposed to measels, after one person was subsequently diagnosed.
MDHB medical officer of health, Dr Rob Weir, said anyone who had been to the event should keep an eye out for symptoms until April 30.
"Measles symptoms initially include fever, runny nose, cough and sore red eyes. After three to five days a rash appears on the head and spreads down the body. "
He said anyone who thinks they may have the disease should avoid public places and work.
"If you think you might have measles I recommend you contact your GP (by phone first) or Healthline on 0800 611116 for more advice. It is very important you tell your GP that you think you might have measles before going in to the surgery," he said.
The Waikato District Health Board has also said people who are without immunisation should get the measels, mumps and rubella vaccine as soon as possible.
They had been notified of five cases of measels in their region, with an infected person still contagious when they visited the festival.