Coronavirus: Why it took several tests for New Zealand's latest case to return positive result

A woman who tested positive for COVID-19 after two of her family members caught the virus underwent several tests over consecutive days for the disease before it was confirmed she had it - and health officials put it down to how changeable the virus is.

The latest case, known as Case D, is the mother of Case C, a toddler who tested positive in the community last week along with their father, Case B. The two were recent returnees who departed the Pullman Hotel managed isolation facility earlier in January.

The woman was placed in self-isolation as a result of these two infections, which is what all close contacts are required to do for 14 days after their last exposure to a positive case. The woman was tested on both January 27 and January 30, the day she began presenting symptoms of the virus. She was then tested twice consecutively on February 1 and February 2, the latter swab returning the positive result.

Director-General of Health Dr Ashley Bloomfield says the reason it took several tests for her to return a positive result is due to the variable nature of COVID-19.

"You have some people who test positive who are completely asymptomatic and not even aware they're infected, others have quite significant symptoms," he said on Thursday.

"But it can take two to three days before they're shedding enough virus, particularly in the throat, that the test picks it up."

He says in this woman's case, it was "good work" by the public health unit since they kept testing her on consecutive days while she was symptomatic.

Arrangements are being made to move her to the Auckland quarantine facility.

There are no new contacts for Case D because she has been in isolation. All other close contacts of Case B and C have repeatedly tested negative, the Ministry of Health says.

Coronavirus: Why it took several tests for New Zealand's latest case to return positive result
Photo credit: Getty Images

COVID-19 Response Minister Chris Hipkins emphasised this latest case is an example of the testing system working as it should.

"As they were a close contact of a previously identified case, the person has been in isolation, and as I've indicated, is being regularly tested. Therefore, the public health risk as a result of this additional positive case is very low," he says.

But he says any time there is a new case, it is a reminder for Kiwis to remain vigilant against the virus. This includes staying home if you're feeling unwell, getting advice from Healthline about a COVID-19 test if you start showing symptoms, using the COVID Tracer app to scan QR codes and turning on Bluetooth, and washing your hands regularly.

In addition to this new case, there were six other COVID-19 cases announced on Thursday, but these are all in managed isolation. Three of these people tested positive on day one of routine testing, two on day three, and one on day eight after they started showing symptoms.