New Zealand has two new cases of Covid-19 today in managed isolation, both travellers from the Philippines.

The first case is a man in his 20s who arrived in New Zealand on July 23 from the Philippines via Hong Kong. He has been in managed isolation at the Rydges in Rotorua and tested negative for Covid-19 around day 3 of his stay.

The man has now been transferred to the Auckland quarantine facility after testing positive around day 12 of his stay.

The second case is a woman in her 40s who arrived in New Zealand on August 1, also from the Philippines via Hong Kong. She has been in managed isolation at the Grand Millennium in Auckland, and tested positive around day 3 of her stay.

The two new cases take the total of active cases in managed isolation facilities to 24, the Ministry of Health said.

None of the patients require hospital-level care.

Housing Minister Megan Woods said the law to charge Kiwis returning to New Zealand has now passed all stages and the fees will come into force mid-August.

More than 35,000 people have now come through border isolation facilities, Air Commodore Digby Webb says.

Health officials considering mask advice

The ministry said it is actively considering its advice to the public on use of masks while considering steps the public could take to be better prepared for a further outbreak.

"The updated World Health Organisation advice is that masks are effective in helping to reduce the spread of Covid-19 when worn by the public where there are cases of community transmission. The WHO also suggests that people should be prepared for the use of masks before the need to use them arises," the ministry said.

"We know that masks have been successfully used overseas to reduce transmission of Covid-19. Masks can be particularly useful when people are in close proximity to each other – including on public transport, in shops, and in other confined spaces.

"If there are further outbreaks of Covid-19, masks will be one important component of our strategy for containing the spread of the virus."

Bloomfield's plea to continue with tracer app

Director-general of health Dr Ashley Bloomfield said tracing contacts of Covid-19 patients as quickly as possible would help stop the virus from spreading in our communities.

"We can't afford for people to wait until there is a case of community transmission to start using the app – we need to quickly be able to isolate any contacts of a future case in our community before the virus spreads out of control," he said.

"By keeping a record of your movements, you will be able to quickly call upon your digital or written diary of your movements to assess whether you may have been exposed to a case of Covid-19.

"Now is the time for New Zealanders to get the app and get in the habit of using it – it is simple, quick and now has extra functionality allowing for manual entries to record where you have been."

The app has now recorded 630,700 users, and 83,337 posters have been created. There have been 1,885,632 poster scans and 39,730 manual entries into the app.

More than 4000 tests processed yesterday

Meanwhile, laboratories processed 4140 tests for Covid-19 yesterday, including 485 swabs taken in managed isolation and quarantine facilities yesterday.

The total number of tests processed to date is now 477,909.

"We would like to thank all New Zealanders who have come forward to be tested – this wider testing is important to ensure there is no undetected community transmission," the ministry said.

Earlier today Bloomfield issued a stern warning for Kiwis to remain ready for a fresh outbreak of the virus.

"We don't want to end up like Melbourne," he told Newstalk ZB's Mike Hosking this morning, referring to the dire situation across the Tasman where hundreds of Covid-19 cases continue to be reported each day in the state of Victoria.

"That's why we've got all our planning and preparation going full steam ahead.

"We've got everything in place we think minimises the risk down to as low as possible, but there are still hundreds of people still working in the facilities and working at the border."

At the weekend, the Government relaunched its next phase of its Covid-19 campaign, telling the public to "be ready."

Today, Bloomfield reiterated the need for Kiwis to remain vigilant and to be prepared for the potential return of the disease in New Zealand.

"So far, we have been successful. But remember that is where the cases came from in Victoria which has led to this huge outbreak [there]," he said.

New Zealand is nearing 100 days of there being no community transmission of the deadly disease.

Anyone with flu-like symptoms is still being urged to stay home and to get tested for coronavirus.

"Our infection control is good," Bloomfield said.

"So we're doing everything we can. But part of keeping New Zealand safe is to do surveillance testing. It's a core part of our programme."