Anyone who was in Queenstown from July 1 to 4 and has since developed Covid-19 symptoms should get tested immediately, health authorities say.
The call comes after fresh information emerged yesterday about the movements of a South Korean visitor who has since tested positive for the virus.
It has raised fears of community transmission in New Zealand — there has been no such case reported in 90 days — but authorities say the risk is low.
The 22-year-old man, who flew out of the country from Christchurch Airport on July 21 and tested positive after arriving in South Korea, was in Queenstown from July 1 to 4.
He also took a bus tour to Milford and joined a boat cruise during that time.
Southern District Health Board medical officer of health Susan Jack said anyone who was in Queenstown on those days and had since developed Covid-19 symptoms should call 0800VIRUS19 if in the southern district, or contact their GP to arrange a test.
Contacts from the man's travel in Queenstown and Fiordland had been identified and were being followed up by health board and ministry contact-tracers.
Public health staff were contacting staff working at businesses in the area at the time the man had visited them, and any contacts experiencing symptoms were being asked to self-isolate until their test results came back, Dr Jack said.
There was a low risk of community transmission from the case, but health authorities were contact-tracing and encouraging testing to be "absolutely sure".
GPs would manage testing through their normal processes, but consideration would be given to setting up community testing centres if needed.
Director-general of Health Ashley Bloomfield yesterday said a second test had confirmed the man's positive result.
Testing of contacts on the man's flights to Christchurch and Queenstown, as well as seven other people considered to be close contacts, had so far returned negative results.
The man's positive test may have arisen from an old infection, or he could have caught the virus while travelling overseas.
The last possibility, that he became infected in New Zealand, was what the ministry was seeking to rule out, Dr Bloomfield said.
Dr Jack said the health board was encouraging GPs to test "one person per 800 of their practice population", which would result in about 400 tests a day across the southern district.
That would "give us good surveillance to pick up any community transmission", Dr Jack said.
She told the Otago Daily Times on Wednesday the district had matched the fall in testing rates across the country, and only about 100 tests were being performed daily by the district's 82 GP practices.
The case was a reminder that Covid-19 was "still very present around the world", and although there had not been community transmission in New Zealand for some months, vigilance was required.
People should be recording their movements and keeping up-to-date contacts for public health officials to find them, she said.
Meanwhile, a man escaped from the Crowne Plaza in Auckland yesterday after tailgating a staff member.
Isolation Facilities Minister Megan Woods said the man was apprehended by police after getting only 50m from the hotel.
One new case of Covid-19 was reported yesterday.