There is no evidence the person who tested positive for Covid-19 in South Korea after travelling from New Zealand was infected here, Health Minister Chris Hipkins says.

But amid an "abundance of caution", officials were contact-tracing two rows in front of and behind the person, who left New Zealand from Christchurch Airport earlier this month.

Hipkins has given the daily Covid-19 update with director general of health Ashley Bloomfield.

The person had been in New Zealand since March 18 on a visitor's visa.

The health ministry hasn't spoken with the person because they're not a New Zealand citizen and so needed to seek permission to do so.

Because they haven't spoken with the individual, all possible close contacts can't yet be identified, said Bloomfield. But 170 had been identified and "the vast majority" had been spoken to.

Bloomfield said there was nothing in community testing in Auckland to indicate that there was any community infection.

The person is also having their movements traced as a precaution but the risk is considered to be low.

They were tested on arrival in South Korea but there was a delay for their result. By yesterday they still hadn't had a second test but health officials were operating on the basis they'd had a second test and it was positive as a precaution.

Hipkins said there was a variety of scenarios here and were still working out which one was correct but were working on a worst-case basis.

One new case

Bloomfield today revealed one new Covid case - a woman in her 20s who travelled from Afghanistan.

She tested negative on day three but returned a weak positive on day 12 and has moved to a quarantine facility.

More than 1100 tests were processed yesterday, with 872 in the community.

Hipkins said the current testing rates still were not at the Government expected them to be.

He said the Health Ministry was working "very, very hard" to work out where the impediment was for the low numbers.

He called it "frustrating" that the numbers weren't high enough.

Bloomfield said the influenza rates were about a third of what they were normally which was impacting test results.

Bloomfield said it was good to see the number of people being tested in the community had increased over the last week.

Bloomfield said the introduction of a throat-swab test had increased uptake.

Bloomfield once again urged New Zealanders to download and use the Covid Tracer app.

Moonlighting nurses

Hipkins said there were robust systems in place for staff working across managed isolation facilities to keep them safe.

From Saturday DHBs will take over the delivery of health services in border facilities, which are currently being provided by contractors.

Anyone working in a facility will have to adhere to a stand-down period and return a negative test before working elsewhere.

The Health Ministry is working in advice around masks if regions were to move up alert levels again.

The ministry also said yesterday it was working on rostering guidelines to limit nurses working across multiple sites, as revealed by the Herald last week.

"There are already in place systems and processes at the managed isolation facilities which are robust and sufficient to keep safe the nurses working there, and the individuals they interact with.

"Nurses are also already provided with guidance on infection control, PPE and procedures to reduce the risk of transmission."

The updated advice will recommend rostering guidelines, limiting staff same-day redeployment to different workplaces and improving managers' knowledge of which staff have secondary employment so additional risk factors can be assessed and managed.

"Nurses are trained professionals, well versed in infection prevention and control and in the Covid-19 context.

"Within managed isolation and quarantine facilities nurses have access to appropriate PPE, follow sound personal hygiene practices and keep to physical distancing requirements. They also have regular health checks and are regularly offered testing for Covid-19, even if they are not symptomatic."