People who travelled on two Interislander ferry trips between Wellington and Picton over the holiday break may have been exposed to measles, after a passenger was diagnosed with the disease.
The person was infectious while travelling across New Zealand between December 28 and January 6, Canterbury DHB says.
They were on the Interislander from Wellington to Picton between 7.45am and 12.30pm on December 28, as well as the return journey between 2.15pm and 5.45pm yesterday.
They were also at the Whare Flat Folk Music Festival in Dunedin between December 30 and January 3, and visited the emergency department at Dunedin Hospital on December 30 between 9am and 1pm.
Anyone who was in those locations at those times may have been exposed, and could be at risk of developing measles, Canterbury DHB says.
"If you are unwell and think it might be measles, stay at home and telephone your General Practice team any time of day or night," Dr Alistair Humphrey says.
"Please don't visit your GP team, other health provider or a hospital in person as this will spread the illness. If it's an emergency call 111."
People who have had two doses of the MMR vaccine, have had measles before, or were born before 1969 are considered immune.
"People are infectious from five days before the onset of the rash until four days after the rash appears, so it is possible to transmit the infection before you feel unwell," Dr Humphrey says.
"People who have been exposed and who are not immune should remain isolated from seven days after their first exposure to 14 days after their last exposure."