The case has been caught early, Bloomfield said.
"We all need to keep playing our part."
The man was potentially infectious on October 14 and 15.
New Plymouth trip
On Wednesday, October 14, he was in New Plymouth working at a ship on the port.
Rooms in which he stayed at in New Plymouth at two different establishments have been deep cleaned.
On Wednesday, he travelled back to Auckland, and was at home on Thursday.
He drove to New Plymouth by himself. That meant there were a limited number of close contacts.
He drove to New Plymouth on Tuesday, October 13, and checked in to a motel. He then worked on the ship on Wednesday, checked into a different accommodation but then decided to drive back to Auckland on Wednesday evening.
There is a very good explanation for where the likely source of infection is, Bloomfield says.
"This is most likely a border-related case ... so far there is no evidence of any onward community transmission."
The Ministry of Health will release the names and details of places and areas the man was at, and pushing out notifications via the Covid tracer app.
Household contacts in isolation
Four household contacts of his are in isolation. Household contacts have been tested. He was not at Ports of Auckland while infectious.
Close contacts from his work there are being scoped - mostly people on the ship he worked on.
The man used masks and gloves when working and was tested within a few hours of developing symptoms on October 16.
The only people he interacted with at the port were security and people on the ship, Bloomfield said.
The man had earlier returned a negative test on October 2, Bloomfield said.
In summary, Bloomfield said the case showed measures were working well to ring-fence any possibility of further spread.
"I know that the re-emergence ... may be unsettling," he said.
"We need to remain vigilant."
Covid-19 was not going away anytime soon, Bloomfield said.
The Ministry of Health recommended people keep using masks on public transport, he said.
Bloomfield was asked why people weren't alerted to this community case earlier. He said once the man had symptoms on Friday morning he was tested and self-isolated, and the two days prior he was not out and about.
Bloomfield contacted the Health Minister just after 6pm yesterday.
"All the people who needed to know were being told, identified, put in isolation and tested.
The man's work made him high risk - he went onboard ships, often for several hours.
He works in electronic maintenance.
Once the man had symptoms he got tested and self-isolated, Bloomfield said. There are a very limited number of close contacts.
The appropriate actions were undertaken" once the man developed symptoms.
"The public should be reassured that the measures around our ports now are very strict ... including PPE and regular testing regimes," Bloomfield said.
The man had four negative tests as part of regular screening testing, and he was due for another one on Friday.
"We are constantly looking at and learning and strengthening our border measures," Bloomfield said.
Both crew and people boarding the ships had to wear PPE, he said.
"In this case we have found a case very early on ... we were able to identify and isolate all the close contacts within a matter of hours.
Asked if there was any consideration of regional lockdown, including New Plymouth, Bloomfield said there wasn't.
The risk to people in New Plymouth was very low, as the man had limited interaction with people at the motel he stayed at, and at the port.
Imported cases today
There are also two imported cases, in managed isolation facilities. And one new historical case - the case mentioned on Friday.
That historical case involves a person who has now recovered and was infected overseas.
One of the cases reported yesterday has been recategorised as under investigation, to see if it his historic
It comes as the NZ Herald obtained a letter from the Auckland Regional Public Health Service, advising that a person has been diagnosed with a notifiable, infectious disease.
The letter says that another person is considered a close contact and may become infectious to others.
It advises the recipient of the letter that this close contact needs to self-isolate at home until receiving a clearance letter.
The Ministry of Health is refusing to comment, or confirm any details.
Auckland Regional Public Health Service said it would not comment until after the ministry's press conference.
