New Zealand health officials said on Sunday they were investigating what they said was probably the country's first community coronavirus case in months, in a woman who recently returned from overseas.
The 56-year-old, who returned to New Zealand on 30 December, tested positive for the virus that causes COVID-19 days after leaving a two-week mandatory quarantine at the border where she had twice tested negative.
"We are working under the assumptions that this is a positive case and that it is a more transmissible variant, either the one identified first in South Africa or the UK, or potentially Brazil - or another transmissible variant," Director-General of Health Ashley Bloomfield told a news conference.
It is not known how the woman was infected or whether the infection is new, Dr Bloomfield said. But since the woman tested positive several days after being released from quarantine and has been at home, the authorities are treating it as a "probable community case".
New Zealand, one of the most successful developed nations in controlling the spread of the pandemic, last recorded a community coronavirus transmission on 18 November, according to the Health Ministry website.
Dr Bloomfield said it was too early to order a further lockdown, with no evidence the woman transmitted the disease to anyone else.
Four close contacts have been identified and while none are symptomatic, each has been ordered to take tests - along with their close contacts.
In a live video on Sunday evening, New Zealand Prime Minister Jacinda Ardern said authorities were working to confirm through genome sequencing whether the woman had a late-onset case of the virus, which she contracted overseas, or whether they became infected while in hotel quarantine.
She said the first option was "not common, but possible" with the results of the testing expected within 24 hours.
"Sometimes there's a tendency to blame, and the message I really want to share here is that the most important thing for us is that people when they are unwell continue to get tested," Ms Ardern said.
"And people are less likely to do that if they feel like they'll be attacked if they happen to be positive. So we really need people not to pile-in on anyone if they do the right thing and get tested."
A tough lockdown and geographical isolation has helped New Zealand virtually eliminate the coronavirus within its borders.
The country of five million people has had only 1,927 confirmed cases. But with the pandemic raging globally, more people are returning to New Zealand with infections, including the new variants, raising concerns the virus may spread in the community again.
The woman, who lives in Northland on New Zealand's North Island, quarantined upon arrival in a managed isolation facility in Auckland where several the highly virulent COVID-19 cases have been recorded in recent weeks, Dr Bloomfield said.
"This is a reminder to all of us that the pandemic continues and that this is a tricky virus," he said.
Social media users rushed to express concern and frustration about the new case, with one user describing the reactions on Twitter as a "collective groan".
On Sunday, there were eight new infections, all returning travellers quarantined at the border, bringing active cases among those quarantined to 79, the ministry said in a statement.
Pressure has been mounting on Prime Minister Jacinda Ardern's government to vaccinate the population, but New Zealand has said the majority of its population would only be vaccinated in the second half of the year.
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With reporting by AAP.
