Four new cases of COVID-19 have been detected at New Zealand's border, with a suspected "weak positive" historic case being investigated by the Ministry of Health.
Each of the new confirmed cases were discovered during routine testing in managed isolation and quarantine (MIQ) facilities.
Two of the imported cases arrived in Auckland from Hong Kong on October 11, while another landed in Christchurch from Peru via Mexico and the US a day earlier. The fourth arrived in Auckland from the Philippines via Hong Kong on October 3.
The suspected historic case is being investigated after the person returned a "weak positive result" upon completion of their stay in MIQ.
The recent returnee from the US was asymptomatic during their 14 days' mandatory isolation and returned two negative tests before being released on September 21.
After becoming unwell this week, the person was tested for COVID-19. The test returned a weak positive result, which the ministry says indicates an old infection.
"We have undertaken further testing today to fully confirm this is a historic infection," a spokesperson said in a statement.
"A PCR test conducted today has returned a negative result. This follow-up testing result strongly suggests that this is a historical infection. We are awaiting further results from other tests including serology.
The spokesperson says precautionary measures are being taken, and the individual has now been transferred to an MIQ facility in Wellington.
They explained cases such as this one can emerge after a person contracts a respiratory illness that is not COVID-19, such as a cold or the flu.
"As we have seen with other cases, individuals can return weak positive tests if they have been infected earlier in the year. This case follows a typical pattern of what we have seen in other historical cases.
"Residual remnants of the virus can be picked up through swabbing, with inflammation often bringing forward virus particles that were not previously picked up."
The four new imported cases brings the total number of confirmed and probable cases in New Zealand to 1880, while the number of active cases climbs to 46.
On Thursday, laboratories processed another 5078 tests, bringing the total number of tests completed to 1,021,931.
There remains no active community cases of COVID-19, although the ministry says more details on the historic case will be shared when they come to light later on Friday.
