But it's unclear if the person lives in Whanganui or had travelled here from the Waikato for a limited period - possibly for work, as suggested by Dyer on Saturday evening.
The location of the facility where the case is isolating is unknown.
Dyer said yesterday it was a DHB-operated facility, but wouldn't confirm the nature of the accommodation, such as whether it was a motel or temporary self-contained unit.
When the DHB was in the process of finalising its self-isolation plans last month, Dyer said they were "looking at a range of options" and would not rule out using motels.
Meanwhile, the Ministry of Health website lists two locations of interest related to the Whanganui case.
The Kai Iwi Beach public toilets and Castlecliff's Polson St Foodmarket are the locations that have been publicly notified, but the Ministry of Health says there are "several" additional exposure events where they have identified close contacts.
Dyer said the DHB and Ministry of Health continued to consider the case "low-risk" to the Whanganui community, but encouraged anyone with symptoms to seek a test.