It takes the Whanganui Health Board region's tally of cases to four confirmed and one probable.
Three cases in the Ruapehu District were confirmed on Saturday.
Public health staff will be in daily contact with the Whanganui couple, who are self-isolating together in one house, to provide them with welfare checks, food and essential supplies.
WDHB chief executive Russell Simpson said the Whanganui Region had done well in following the Level 4 Alert restrictions, keeping to their bubble and adhering to the two metre rule.
"I want to reiterate to the community how vitally important it is that people stay at home so we can contain COVID-19, especially now with one more confirmed case in our region," he said.
Simpson said the emergency response is well prepared, with trained people managing cases to prevent the spread of COVID-19 and to protect the health of people in our region.
"The community has been doing a great job, staying home and only leaving for essential services, but we especially urge people not to move in and out of our region. We hope this will help keep numbers of cases low and minimise the impact of Covid-19 on people and whānau in the Whanganui Region, especially older people and those with other health conditions."
Meanwhile, one more case of Covid-19 was confirmed in Taranaki on Thursday bringing the region's total to 15.
