"They should not go to their general practice or turn up at an Emergency Department if they are unwell as they will risk infecting more people.
"Measles is highly contagious: If one person has it 90 per cent of the people close to that person who are not immune will also become infected."
Cases of the illness have been confirmed in Queenstown, Wanaka, Canterbury and Nelson-Marlborough.
Investigations are into the source of the outbreak are continuing, however the person who sparked it may have had a relatively mild illness and fully recovered.
Public Health Units at Nelson Marlborough, Southern and Canterbury DHBs were identifying the close contacts of infected people and working with affected individuals and work places to provide advice to staff.
Instead of going to the doctors people who believe they may have measles should phone their GP after hours or call Healthline on 0800 611 116.
About measles
• Measles is a notifiable disease, which means any confirmed cases must be reported to government agencies.
• It is highly contagious and is spread through coughing and sneezing.
• Early symptoms include a dry cough, runny nose, temperature of more than 38.5 C and feeling very unwell.
• After four or five days a rash appears, it usually starts on the sufferer's face, then moves down to the chest and arms.
• Those confirmed to have the disease are infectious from five days before the onset of the rash to five days after the rash starts.
• People should stay in isolation while they're infectious - this means staying home from school or work and not having contact with unimmunised people.
• People are considered immune if they have had two doses of MMR (measles, mumps, rubella) vaccine, have had a measles illness previously, or were born before 1969.
• More information about measles is available at www.health.govt.nz/your-health/conditions-and-treatments/diseases-and-illnesses/measles