An 18 year-old female who attends a college is the third person in a fortnight to be diagnosed with measles in Canterbury.
Investigations show the first case and the most recent case happened to be at Christchurch Hospital's emergency department at the same time late last month, showing just how infectious the virus is.
Canterbury Medical Officer of Health Dr Alistair Humphrey says the woman who is the latest to be diagnosed also visited the emergency department on Saturday and again on Sunday.
Patients and visitors who are not fully vaccinated with MMR and were in the waiting room any time at the weekend after 10am on Saturday are being urged to contact their GP and get vaccinated immediately.
Staff who were in the area at the time are also being notified. People born before 1969 are considered immune and need not get vaccinated.
An 11-year-old child who was confirmed with measles last week is now recovering at home.
Unvaccinated students at the school and at a church the child attended have been sent directives to remain at home for the rest of this week.
A 30-year-old man who was the first case confirmed in Christchurch this year, has since recovered.
The 18-year-old woman attended a college for two days last week, and fellow attendees have been notified.