Three cases of mumps have been confirmed in Hawke's Bay.
One was a student from Hastings Boys' High School, while the other two cases are adults.
The cases have prompted health officials to urge parents to check their children's immunisation status.
Hawke's Bay District Health Board spokeswoman Dr Rachel Eyre said Hastings Boys' High School had worked swiftly with health officials after the diagnosis.
Important health advice had been sent out to all parents and caregivers and wider school communities.
"Mumps is a highly infections viral infection, spread by breathing, sneezing and coughing and can spread quickly among those who are not immune, particularly in schools," Eyre saide.
Thie outbreak was a timely reminder for parents and carers to check their children were up-to-date with immunisations.
"Be aware that if your child is developing a fever or has swelling of the glands around the checks or jaw, to stay home and phone your doctor in the first instance, or Heathline on 0800 611 116."
Eyre said it was important people with suspected mumps stayed away from school, work or community gatherings until five days after swelling developed or until well, whichever was sooner.
"If you were born after 1981 and have never had mumps or mumps/MMR immunisation, you need to see your family doctor," Eyre said. Two documented doses was required to prove immunity.
"The sooner the free immunisation is given, the more likely it is to protect you."
Unvaccinated adolescents and adults are most at risk, and are more likely to experience severe mumps disease and complications.
Public health officials had advised health profession to be on the alert for mumps.