New Zealand now has 52 confirmed cases of Covid-19, including two cases which have no link to overseas travel.
"At this point, we cannot rule out a risk of community transmission in these [two] cases," Director-General of Health Ashley Bloomfield said this morning.
"We always knew that cases not linked to travel could happen and we are prepared for that," he said.
A further 13 positive tests were confirmed in the past 24 hours, the biggest jump in cases in a single day so far.
Earlier, the Ministry of Health released a miscalculated statement saying there were 14 new cases, but this was corrected.
In all, 1500 tests were processed in that period, Bloomfield said.
Of the confirmed cases, three people were in hospital and in a stable condition.
The new cases are in Auckland, Waikato, Taranaki, Manawatu, Taupō, Wellington, and Nelson.
Of the cases not linked to travel, one is in Auckland and one in Wairarapa.
Neither of the people had travelled overseas, so their relatives and friends' travel was being checked. The partner of the Auckland person had regular contact with people who travelled frequently. In the Wairarapa case, there was no clear link to any travel.
It was now more important than ever to track and trace individuals who had been in contact with confirmed cases and get them into isolation, Bloomfield said.
Testing for Covid-19 has ramped up as more people returned from overseas, and would continue to do so. That would help detect if there had been community transmission in New Zealand, Bloomfield said.
New Zealand's rate of 1500 tests a day compared to South Korea's rate of 10,000 a day for a population 10 times larger.
The Ruby Princess cruise ship, which has just arrived in Sydney, had three confirmed Covid-19 cases, and 56 New Zealanders on board are being contacted. Of that total, 28 have returned to New Zealand.
All of the people on that ship were being considered close contacts and were being monitored daily by health officials.
The update comes before a speech by Prime Minister Jacinda Ardern, which will be broadcast from the Beehive at midday.
PLAN FOR CLOSURES
Speaking on Newshub Nation this morning, Director-General of Health Ashley Bloomfield said if community transmission was confirmed, further measures would be introduced to encourage physical distancing.
That could include asking shops, bars and restaurants and close - as has been done in the UK and USA.
If an outbreak was localised, that specific region could be locked down with no travel allowed in or out. People who had left that area in the last few days would also be required to self-isolate.
"That could be a very effective way of not only stopping transmission in that community but preventing any onward transmission."
Existing measures like contact tracing, physical distancing, self-isolation and bans on large gatherings would also continue.
Some individuals and groups have been flouting bans on large gatherings. Earlier this week, Destiny Church said it would go ahead with church services this weekend.
Bloomfield said the church would be rethinking that position.
"We also know that the Government does have powers to enforce the 100 maximum on gatherings. So if needs be, those powers will be used."
Education Minister Chris Hipkins said the decision to leave New Zealand schools open was based on the best medical advice, and the fact there was no evidence of community transmission at this stage.
Plans were in place if spread in the community was confirmed. Those could include bringing school holidays forward and extending them.
The Government was also in talks with telecommunications companies about access to broadband for all students, and possibly removing data caps to allow digital learning in all homes.
Further measures to contain Covid-19 were announced yesterday, including temporary closure of libraries, art galleries, museums and university lecture theatres.
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New Zealand closed its borders to non-residents and non-citizens on Friday, and other countries have gone into lockdown with citizens told to return home.
Italy, with 60 million citizens, has recorded 3405 deaths, exceeding the 3248 in China, a country with a population 20 times larger.
It took three months to reach 100,000 coronavirus cases worldwide. The second 100,000 took only 12 days.
Travel details of 14 new cases:
Case number 53: Auckland, aged in 50s, still under investigation
Case number 52: Nelson, aged in 20s, travel related, however international flights outside of infectious period. Domestic flights: Auckland to Nelson on 16 March – flight 5065
Case number 51: Nelson, aged in 60s, still under investigation
Case number 50: Manawatu, aged in 20s, Doha to Auckland on 14 March – flight QR0920. Auckland to Palmerston North on 16 March – flight NZ5107
Case number 49: Manawatū, aged in 40s. Travel related. Queenstown to Christchurch on 13 March – flight NZ642. Christchurch to Palmerston North on 13 March – flight details unclear
Case number 48: Taupō, aged in 50s, Dubai to Auckland on 10 March – flight EK0448
Case number 47: Auckland, aged in 70s, Dunedin to Auckland on 16 March – flight NZ674
Case number 46: Wellington, aged in 30s, Dubai to Auckland on 12 March – flight EK44. Auckland to Wellington on 12 March – flight NZ433
Case number 45: Wellington, aged in 50s. Travel related, however international flights outside of infectious period. Domestic flights: Auckland to Wellington on 8 March – flight NZ449, Wellington to Hamilton on 12 March – flight NZ5810, Hamilton to Wellington on 13 March – flight NZ5823.
Case number 44: Wellington, aged in 50s, Sydney to Wellington on 14 March – flight QF161.
Case number 43: Waikato, aged in 60s, Singapore to Auckland on 13 March – flight SQ0285.
Case number 42: Auckland, aged in 60s. Cruise ship travel. Domestic flights – Dunedin to Auckland on 15 March – flight NZ670.
Case number 41: Taranaki, aged in 40s. Dubai to Auckland on 8 March – flight EK448. Auckland to New Plymouth on 9 March – flight NZ8041.
Case number 40: Wellington Region, aged in 50s. Travel related, however flights outside of infectious period.