Like other returning travellers, she spent 14 days in quarantine and twice tested negative before being returning home on 13 January. She later developed mild symptoms and tested positive.
He said health officials will conduct genome testing but are working under the assumption that the case is a more transmissible variant of the virus.
He said they are investigating to see whether its possible she caught the disease from another returning traveler who was staying in the same quarantine facility.
Dr Bloomfield said the woman and her husband were now in self-isolation in their home south of Whangarei, and the woman did not require hospital care.
New Zealand has eliminated community transmission of the virus, at least for now. Bloomfield said officials are ramping up contact tracing and testing efforts and hope to have more information about the case in the coming days.