Doctors are scrambling to deal with an unrelenting and unprecedented mumps outbreak that has landed teenagers in hospital and led to one developing meningitis.
So far there have been more than 130 mumps cases in Auckland in the first six months of this year compared with just 35 for last year.
The Auckland Regional Public Health Service has blamed low vaccination rates for fuelling the city's outbreak.
The service's clinical director Dr Julia Peters said some of those 135 mumps patients had developed severe complications and ended up in hospital.
Some teenage males were suffering from severe pain and swelling in their testicles, which in rare cases could result in infertility.
Some females had experienced ovarian inflammation and one person had developed meningitis. The infected patient had since recovered.
"This year we have had over 130 mumps cases in Auckland compared with 35 last year. Unfortunately 80 per cent of the current cases were not fully vaccinated. It is disappointing because mumps is a preventable and serious disease," said Peters.
"Most recover from this disease. However, in the last six months a number of people have suffered from severe complications caused by mumps."
She said parents should check with family doctors to make sure measles, mumps and rubella vaccinations were up to date.
Nearly three-quarters of the cases were occurring in children and teens aged 10 to 19.
Peters said because mumps could spread quickly among those who were not immune it took just one child with mumps at a secondary school to cause an outbreak.
It was concerning immunity at that age group was well below the national average.
"If parents do not organise vaccination quickly, their child may be excluded from school. We are in the midst of an outbreak and already many students are scrambling to catch up on school work after missing school for several weeks," said Peters.
Non-immune pregnant women who caught the disease were also at risk of miscarriage in the first three months. In rare cases mumps could cause permanent hearing loss.
The regional health service was working with primary care, early childhood, schools and tertiary institutions to provide support and resources to minimise the spread of mumps.