Ten cases of measles have been confirmed by the Ministry of Health.
One of the confirmed cases is in Auckland and nine are in Turangi and Taupo.
Another case is under investigation in Turangi/Taupo.
The Ministry of Health acting deputy director of public health, Harriette Carr, said the Auckland person and three of the nine confirmed in Turangi/Taupo attended the 2013 World Supremacy Battleground hip-hop competition in Sydney last month.
The remaining cases were family or known to those who had been at the festival. No one had yet been hospitalised but all those who were infectious were being kept isolated at home.