A DHB spokesperson said numbers started to climb when two Kiwi women, who tested positive for Covid-19, were allowed to leave their isolation in Auckland last month on compassionate grounds and travel to Wellington.
From June 12 numbers began to climb from around 20 people per day to around 80 people, with one day around 90 people presenting themselves at the CBAC he said.
But in the last two weeks numbers have returned to around 20 people a day with things "clearly quieting down".
Of the 91 people tested in the past week, 48 were swabbed at the community-based assessment centre at Whanganui Hospital.
Only one CBAC remains at the hospital campus and is open Monday to Friday 8am to 4.30pm and 10am to 3pm on weekends.
GP practices and iwi providers such as Te Oranganui in Wicksteed St also provide swabbing.
Rural communities can also be swabbed at their local GP practice but are asked to phone first.
"People should continue to regularly wash their hands or use hand sanitiser and to dry them thoroughly; cover coughs and sneezes by using the crook of your elbow," WDHB said.
The DHB is also encouraging people to download the NZ Covid Tracer app and scan the QR code that is displayed at the entrance of the hospital and at local businesses, offices and shops around town.
"This will be a huge help if we need to contact trace people if we have another positive case."
Anyone with flu-like symptoms, a cough, sore throat, fever, shortness of breath, runny nose, sneezing or loss of sense of smell should stay home and phone their GP to get assessed or visit the community-based assessment centre.