The Director-General of Health says a ship now bound for Brisbane is believed to be the most likely source of transmission in the latest COVID-19 case in New Zealand.

A marine electronics engineer tested positive for COVID-19, the Ministry of Health confirmed yesterday.

The man had been working on a ship at Port of Taranaki on Wednesday, October 14. He became symptomatic on Friday, October 16, and sought a test.

The man had been getting regular testing, he tested negative on October 2.

The Ministry of Health says the risk of community transmission is low because the man had limited contact with members of the public.

His household contacts are self-isolating and other close contacts are being investigated.

Director-General of Health Dr Ashley Bloomfield told Morning Report it's unlikely the ship, now anchored in at sea awaiting clearance to dock in Napier, is the source of the transmission.

"There's one (ship) in particular that he worked on around October 12 and 13 that is considered the most likely one that he might have been infected on.

"That vessel's now departed New Zealand, so there'll be some work with authorities, actually it's on its way to Brisbane, so there's work with authorities there to be done, they've already been notified that it's on the way."

Dr Bloomfield is unaware of how long the ship (bound for Brisbane) had been at sea, but crew onboard are not allowed to come on shore unless certain protocols have been met beforehand.

"Even if a ship has been at sea for 14 days, because of the nature of that closed environment ... the close quarters within which the crew and or passengers are living, it means that the virus can sort of bounce around for much longer than 14 days and you may have ... the whole crew with negative tests someone could still be incubating the virus."

Dr Bloomfield says the man had been working on the ship in New Plymouth for six hours.

The man also stayed at a motel and hotel during his stay in New Plymouth. The Devon Hotel, where he stayed, had been thoroughly cleaned, its owner said.

Dr Bloomfield says investigations into the where the case came from are ongoing.

"The other thing we are hoping to get through today is the whole genome sequencing on the case's COVID-19 test because it will give us a hint about where the origin of his infection might be."

Dr Bloomfield says the MoH will consider whether the time between testing of port workers needs to be shortened because of this latest case.

More cases like this will keep popping up - Michael Baker

University of Otago epidemiologist Professor Michael Baker told First Up to expect similar cases to this one in the future.

"The pandemic is just intensifying globally, New Zealand has many connections with the outside world via airports, sea ports and arriving passengers and all of those situations that can allow the virus to get back into New Zealand.

"If we look now at the pattern of the last couple of months, we've had four other examples of the virus coming across the border, assuming the large Auckland outbreak was also introduced in this way, so this is really the fifth example of the last two to three months.

"We are seeing a pattern, it's not probably going to be a very predictable pattern, but I guess the good news is that the last four of these breaches have all been very small and picked up quickly."

Michael Baker says by all accounts, the man did everything right and should be commended for his pragmatism.

-RNZ