A total of 145 Whanganui residents presented at the city's main testing station over Saturday and Sunday - the majority of which came after the announcement of the case on Saturday evening, the DHB said.
The DHB is yet to say how many tests were carried out in the days before the case was discovered.
A DHB spokesperson said Whanganui residents needed to be patient at testing clinics, saying staff were under extreme pressure and delays could be expected.
The jump in demand for testing comes after the Ministry of Health published the first two locations of interest in the city on Sunday.
Castlecliff's Polson St Foodmarket was visited by the case between 1.15pm and 1.45pm last Friday, while the public toilets at Kai Iwi Beach are also a location of interest after the case visited between the hours of 12pm on Tuesday November 30 and 6pm on Thursday December 2.
In the Ministry of Health's update on Sunday, a spokesperson said that "a number of" additional locations would be added to the Ministry's website that afternoon, but none have yet been posted.
The Ministry has been asked if there are any additional locations.