Another case of measles has been confirmed in Levin, this time at a day care centre.
It's the 10th case in the area, with nearby Waiopehu College which closed on May 20 after a student came down with the virus.
Dozens of cases have been confirmed in Waikato, Northland and Nelson recently after one person caught the virus at a kapa haka festival in Hamilton.
The MidCentral Public Health Service is now working with Lollipops Educare to follow up with contacts and stop the measles spreading.
Medical Officer of Health Dr Rob Weir says those who haven't been vaccinated -- or are too young to be immunised -- have been asked to stay in isolation for 14 days.
"Since this outbreak began, we have had fantastic support from the community in Horowhenua, and it is great to see that people are taking the situation seriously. Given the time it takes for measles to incubate and begin showing symptoms, there is the potential for this situation to continue for some time.
"We don't want people to worry unnecessarily about this situation, as the initial work done to isolate contacts has kept this fairly confined to specific groups, but it is important to remain on alert for any potential symptoms.
"As this continues, we will ensure everyone is updated, and continue to support individuals, families and community groups as necessary."