The Auckland MIQ worker returned a positive test result as part of routine testing.
The Ministry of Health has now confirmed that the worker has caught the Omicron variant.
More than 50 close contacts have so far been identified.
All of the case's seven household contacts identified have already been contacted, isolated and tested, and returned a negative result.
The case and one household contact are now isolating in a MIQ facility. The remaining household contacts are isolating at locations in Auckland and Taupō.
A further 48 close contacts are in the process of being contacted; 15 of them have returned a negative test, including five in Taupō.
The worker, who was infectious from 10 January, took two bus services in Auckland and visited a supermarket and four other stores in the city.
Those locations, and areas of the MIQ facility are considered high-risk, and the Ministry of Health says anyone in Auckland with symptoms should get tested.
All the latest locations of interest can be found on the Ministry of Health's website.
There are 25 new cases of Covid-19 in the community today, and 43 in MIQ.