A mumps outbreak in the Auckland region is continuing to drive up the number of reported cases nationwide - with reports of the illness registered over the first four months of this year more than triple that of the same period last year.
However, health officials suspect an outbreak declared back in 2016 has peaked and say the number of cases recorded is declining monthly.
Figures from New Zealand's Institute of Environmental Science and Research document 313 cases of confirmed, probable and suspected mumps over the first four months of this year.
This is in contrast to a total of 88 cases over the same period last year.
Additionally, more than twice as many New Zealanders had been struck with measles over the first four months of this year than the same time last year - there were 25 reported cases in comparison to 2017's 10 cases.
Public health physician Jill Sherwood said the mumps outbreak in Auckland had peaked in October last year.
"There were 276 cases in that one month - that was the peak."
"So far this year, while it's well above what we normally would have in a non-outbreak period ... it's been going down every month since early this year."
Most cases had occurred in West Auckland, and more than half were students aged between 10 and 19.
Sherwood said the high occurrence of cases in Auckland could largely be attributed to mumps circulating in Pacific communities.
"Several of the Pacific territories use a single antigen measles vaccine and they don't vaccinate against mumps and rubella in a combined vaccine."
The Ministry of Health had measures in place to overcome this.
Director of public health Dr Caroline McElnay said mumps vaccines were free for anyone who had not had the two jabs when they were younger.
This covered people who might not have grown up in New Zealand, she said, as well as those whose parents might have decided not to have them immunised growing up.
"When we look at the cases we are seeing, they were really in that older adolescent or young adult age bracket," McElnay said.
In New Zealand, children are vaccinated against measles, mumps and rubella at 15 months and 4 years.
Measles, McElnay said, was a different picture.
The highly contagious illness is brought into the country. It was suspected the latest outbreak spread from an initial carrier who passed through Christchurch and Queenstown airports.
McElnay said health services hoped the outbreak had now been contained.
"At this stage we're waiting to see if we get another case."
The high figures followed news of a whooping cough outbreak in New Zealand.
Earlier this week Auckland school ACG Parnell confirmed one of its students has been diagnosed with whooping cough.
School deputy principal Julie Kerr said whooping cough, also known as pertussis, was a notifiable disease which required the school to alert the parents of students who had been in close contact with the affected student.
The Ministry of Health declared a national outbreak of the disease on December 1 last year.
In the four months from January 1 to May 4 there were 1412 confirmed, probable and suspected cases of whooping cough reported, Institute of Environmental Science and Research (ESR) figures showed.
That was more than double the number of cases reported in the same period last year.
• Early symptoms of mumps include fever, headache, muscle aches, tiredness, and loss of appetite.
• The best way to protect against mumps is to be vaccinated with two doses of the measles-mumps-rubella (MMR) vaccine.
• In New Zealand the MMR vaccination is given at age 15 months and again at 4 years.
• The virus is often spread from an infected person by saliva or mucous droplets when coughing, sneezing, or talking.
• 2 doses of the measles vaccine provides the most effective protection from measles. After 2 doses of the MMR vaccine, more than 95% of people are protected from measles.
• Measles can be life threatening: about 1 in 10 people with measles will need hospital treatment.
• Vaccination is particularly important if you are planning to travel anywhere overseas - the illness does not originate in New Zealand.
Source: Ministry of Health