A Northern Territory couple who had disembarked from the Ruby Princess cruise ship in Sydney and flew to Darwin have tested positive to COVID-19, bringing the territory's total cases to five.

The Northern Territory Health Department confirmed the couple, who are from Darwin, immediately went into isolation upon their return home yesterday afternoon and underwent testing for the virus.

Today the couple has been admitted to the Royal Darwin Hospital in a stable condition after tests came back positive.

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The Ruby Princess in Sydney this week. (Getty)

NT Health said when the couple disembarked in Sydney there was no confirmed cases of coronavirus on the ship.

Health Minister Natasha Fyles said they flew from Sydney to Darwin on flight JQ672 and were picked up by a family member upon their arrival and immediately self-isolated at home.

"These people have done the right thing, they have followed the guidelines... They were allowed to transit home," Ms Fyles said.

"Once they got to the Northern Territory, they have self-isolated and the only contact they have had is with family and friends who had been helping them."

Director of NT's Centtre For Disease Control Vicki Krause and NT Health Minister Natasha Fyles today. (Aisley Koch/9 News)

It comes after two people — a man in his 30s who returned from Europe and a 21-year-old female who returned from the US — tested positive to COVID-19 yesterday after they arrived in the territory on separate flights.

A 52-year-old man from Sydney remains in isolation at the Royal Darwin Hospital and is awaiting clearance from two tests before he can return home.

Director of the Centre for Disease Control Vicki Krause said passengers two rows in front and behind the cruise ship couple would be contacted to undergo testing.

Ms Krause said it would be a matter of "wait and see" as to how quickly the virus spreads in the NT.

"The five cases we've had so far have been acquired from overseas," she said.

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"We've had a bit of a slow start because we are some distance from the east coast… but we are expecting to see more cases."

Ms Fyles said it was important people continued to isolate themselves and call the territory's coronavirus hotline on 1800 008 002 for advice.

"The message is clear… please don't put the broader community at risk… if they need something, arrangements can be made to get it to them," she said.

"We encourage anyone if you are not feeling well, isolate yourself and call through."