Health authorities say three people have been diagnosed mumps in Tauranga this month.
However, there were concerns more people might unwittingly be carrying, and passing, on the virus.
Toi Te Ora Public Health Organisation chief medical officer Neil de Wet said mumps could have serious health complications including swelling of the brain, loss of hearing, and potential infertility in young men but these were rare.
Dr de Wet said there had been an increase in mumps cases in New Zealand in the past year but most of these were in Auckland. Up until last week, there had been three confirmed cases in the Bay of Plenty District Health Board area.
"In the past, our immunisation rates have been very low so people who are now in those two age groups - 10 to 19 and 20 to 29 - historically they had low immunisation rates. It's not surprising that we are seeing most cases in these age groups."
The Auckland Regional Public Health Service had been notified of 300 cases of mumps from January 1 to September 4 this year.
Dr de Wet said because of the high mumps numbers nationally, it was hard to establish Auckland links to the local cases.
"We do have mumps in our community and people can be asymptomatic, especially younger children. They might not be symptomatic so not every case will be diagnosed," Dr de Wet.
Mumps symptoms include headaches, a general feeling of unwellness and swelling of the jaw area.
"For most people, this is an unpleasant illness that will get better on its own after about a week."
Mumps can be spread from person to person throughout the air by coughing and sneezing. The MMR vaccine which is part of routine childhood vaccines prevents mumps, as well as measles and rubella.
Anyone who feels they might be sick or at risk is encouraged to phone their family doctor to arrange an appointment at a time unlikely to infect anyone else, Dr de Wet said.
The last mumps epidemic in New Zealand was in 1994, with 188 hospitalisations. Twenty to 30 cases of mumps were still notified each year; about half are in children under 10 years of age.
Auckland medical officer of health Dr Josephine Herman said mumps was now at large in the local community "and the only way we can stop this spreading further is to achieve high levels of MMR vaccination in the population".
What is mumps?
Mumps is a viral illness, which can cause swelling and tenderness of one or more salivary (parotid) glands. Some people with mumps have no symptoms and others may only have symptoms in other organs, for example, meningitis or inflammation of the testicles (orchitis).
Source - immune.org.nz