Adults and parents with children at Waipukurau Primary School in Central Hawke's Bay are being asked to check their immunisation status following a confirmed case of mumps at the school.
Medical officer of Health Dr Rachel Eyre said: "Mumps is a highly infectious viral infection, spread by breathing, sneezing and coughing. People with mumps may suffer swelling of testicles or ovaries, hearing loss, breathing difficulties and rarely, brain inflammation.
It can affect babies, children or adults, she said.
"If you suspect you or your child is developing a fever or has swelling of glands around the cheeks or jaw, phone your own doctor or Healthline (0800 611 116).
"Please stay away from school, work or community gatherings until five days after swelling develops or until well, whichever is sooner."
If you were born after 1981 and have never had mumps or mumps/MMR immunisation (two documented doses is required to prove immunity), you need to see your family doctor.
"The sooner the free immunisation is given, the more likely it is to protect you," Dr Eyre said.
A letter has gone to staff and parents at the school advising them that if they aren't immune there is a risk of passing the infection on to others even before developing symptoms.
Dr Eyre said it was Ministry of Health policy for non-immune adults and children to stay away from school, work or community gatherings until 26 days after last exposure which is 2 October (beginning of the school holidays).
"We know this may create difficulties for some families, but our priority must be to prevent further spread of the virus.
"We have been advised that the school will work with affected families to ensure pupils who need to stay home are supported in their learning.
"Even if you get immunised immediately you may still develop mumps because immunisation may be too late to prevent the disease.
"However, it will protect against future infection and reduce the risk of complications.
"Fortunately in Hawke's Bay we have high rates of immunisation coverage, which should help prevent the spread of the disease in our region."