Auckland's in the middle of the largest mumps outbreak for 23 years.
The city's Public Health Service has been notified of 740 cases this year.
Medical officer of health Josephine Herman said this is the worst outbreak since 1994.
"This is quite a large outbreak and something that we are very concerned about and trying our best to implement public health measures to contain it."
Mumps is a viral infection passed in a similar way to colds, and symptoms include fever, headache, muscle aches, and most notably swelling of the salivary gland.
The illness is back in the headlines after it was announced Reiko Ioane might miss the next All Blacks game due to a case of mumps.
Herman said the solution is to get the MMR vaccine, cover coughs, and wash hands.