The mumps outbreak hitting the country has spread to Whanganui.
Medical officer of health Patrick O'Connor said cases had been confirmed in the city - two adults and one child.
More than 900 cases of mumps have now been notified nationally this year, most of them in Auckland where there have been 740 cases.
Those most at risk in the present outbreak are aged 15-24 years. All Black wing Rieko Ioane, 20, has the mumps and is in doubt for the test against France in Paris this weekend.
Mumps is caused by a virus which can spread when an infected person coughs or sneezes, or passes it on through their saliva when kissing or sharing food and drink. Antibiotics will not treat the infection or prevent spread.
Dr O'Connor said the best protection was the MMR (measles, mumps, rubella) vaccine and he urged people to check their immunisations are up to date. Children have this vaccine at age 15 months and 4 years and anyone in New Zealand born since 1969 was entitled to two free doses.
Complications can include meningitis or encephalitis, with young children most at risk.
Dr O'Connor said the usual early signs were fever and headache. Then after about two days salivary glands on one or both sides of the jaw might become swollen and sore.
"A person with mumps is considered infectious from two days before the facial swelling until five days after," Dr O'Connor said.
"Anyone with these symptoms is asked to stay away from other people for five days after the swelling."
If another person was infected, it would usually take 16-18 days until that person becames unwell, but this incubation period could be as long as 12-25 days.
"If someone is unwell with swelling on the side of their face, they should isolate themselves and contact their doctor who can check for mumps by swabbing saliva on the inside of their cheek.
"If you are seeing your doctor for this reason, it helps to phone ahead as this reduces the chance of infecting someone else."