"Ultimately I know this decision is hugely disappointing. I know it will have an impact on a number of communities ... but we are making this decision in the best interest of New Zealanders."
Social distancing was the "new normal" and should apply to everyone's actions, including visiting bars and restaurants.
The Government is not shutting schools or universities, with the Prime Minister saying "that is not where New Zealand is at".
There is no plan at this stage to cancel any school holidays.
But the latest Ministry of Education advice advises schools to keep students at least 1.5 metres apart at assemblies, and to reconsider school camps unless they have the ability to isolate any student who becomes ill and have "personal protective equipment and the ability to clean hard surfaces".
Social distancing is the "new normal" and should apply to everyone's actions, including visiting bars and restaurants.
"If you're close enough for someone to spit on you when you talk, you're too close," the Prime Minister said.
"We're asking you to work together, but just with a little bit of distance between you."
But Ardern said: "No one needs to conduct a run on their supermarket".
The day New Zealand's first case of coronavirus was confirmed, shoppers descended on supermarkets in Auckland stocking up on items like toilet paper, face masks, hand sanitiser and non-perishable foods.
"It's worth remembering that we've had travel restrictions on China for over a month, and those supply routes continue."
• People who become sick within a month of travelling overseas are encouraged to seek medical advice and phone Healthline on 0800 358 5453 or a doctor. It is important to mention recent travel history, and any known contact with someone with a confirmed case of Covid-19.
Ardern said there would be "zero-tolerance" for travelers who did not follow the recently announced travel restrictions and self-isolate, and anyone refusing to self-isolate was "not welcome" in New Zealand.
Ministers would use the Immigration Act to deport people on visitors visas, and deportation was a serious blight on someone's record.
For New Zealanders, anyone who refuses to self-isolate when required could be placed in a medical facility and have a police officer placed at their door to prevent them escaping.
People signing forms about self-isolation could be turned into statutory declarations, where violating the terms could lead to a fine of $2000 and three months imprisonment.
What does it mean to self-isolate?
You should avoid situations where you may come in close contact with others (face-to-face contact closer than one metre for more than 15 minutes), such as social gatherings, work, school, child-care/pre-school centres, university, polytechnic and other education providers, faith-based gatherings, aged-care and health-care facilities, prisons, sports gatherings, restaurants and all public gatherings.
If you have been exposed, it may take up to two weeks for symptoms to present.
Ardern said a range of measures to assist those in self-isolation would be announced this week.
Community support to those unable to support themselves would be increased.
A public information campaign will be launched, the Finance Minister will announce a business continuity package and the Health Minister will announce a suite of additional health measures.
Do I have to self-isolate if someone at my home is doing so?
The Ministry of Health advice is that other residents at the home who have not travelled do not need to self-isolate so long as precautions are followed. Although your employer may have its own set of rules.
Minimise close contact with the other residents by avoiding situations where you may have face-to-face contact closer than 1 metre for more than 15 minutes.
You should not share dishes, drinking glasses, cups, eating utensils, towels, pillows or other items with other people in your home. After using these items, you should wash them thoroughly with soap and water.
If you are unsure if you should be self-isolating, or if you do not know where you can go, you can contact Healthline for free on 0800 358 5453.
Will I still be paid if I self isolate?
• If a worker in self-isolation does not feel sick and is willing and able, they can offer to work from home and agree with the employer to do so. They will be paid normally.
• If an employee, who has been advised to self-isolate under Ministry of Health guidelines for Covid-19, can't practicably work from home, then special paid leave should be considered. Other forms of paid leave can be considered (such as paid sick leave) and used by agreement between the employer and the employee.
• If the person is sick, or needs to care for a sick dependant, paid sick leave (and anticipated sick leave) may be used. If paid sick leave is not available, paid special leave should be considered. Other forms of paid leave can be used by agreement between the employer and the employee.
• Contractor pay and leave is not covered by this guidance. Employers and contractors can agree to any payment arrangements they wish to.
How else could it affect my job?
There has been an increase in employees working at home since the outbreak. In the US, Twitter, Apple, Google, and other large companies have asked employees to work from home to slow the spread.
Even if you are not sel-isolating, you may be asked to work from home as businesses prepare for a "worst case scenario" and make sure enough of their workforce are set up to do so if they need to.
More than 1200 Auckland-based Vodafone permanent staff worked from home in a test to simulate worst-case Covid-19 scenarios.
Ardern has said she has preliminary advice from Treasury that the impact could be greater than the impact of the GFC.
The Reserve Bank of New Zealand on Monday delivered a shock 0.75 per cent cut to the official cash rate (OCR) this morning, citing Covid-19 as the reason.
It now sits at 0.25 per cent – the lowest it has ever been.
The latest confirmed cases are a man in Wellington, who came from Australia, and a woman travelling from Denmark via Doha.
A number of additional cases are under investigation, and hundreds have tested negative for the virus.
Read more: What we know about the right cases.
What is the situation around the world?
As of early Monday morning, there were more than 156,000 cases of coronavirus globally and 5800 deaths. More than 74,000 of the 156,000 people have recovered.
The World Health Organisation declared last week the global coronavirus crisis was now a pandemic, which sparked Trump's announcement flights from Europe would be banned and also for shares to dive for the second time on Wall St.
Some countries around the world, including the US, France, Ireland, Norway, Turkey, Jamaica and Israel, have also begun closing schools and universities.
Some states in the US - and other countries - are beginning to ban gatherings of large people including New York, limiting it to 500 people.
Disneyland has closed its parks temporarily until the end of the month and New York theatre mecca, Broadway has closed. And Nepal's Government has cancelled the Everest expedition season.
Many sports events have been cancelled including Super Rugby, Six Nations Rugby and English Premier League football. The Football Association of Ireland suspended all games until March 29 while the Euroleague and La Liga, the Spanish premier league, suspended their competitions temporarily.
Many cruises companies also announced suspensions.
Where did coronavirus come from?
It was first reported in Wuhan City, Hubei Province, China. The live animal market, the Huanan Seafood Wholesale Market, is suspected as the original source but has not been confirmed.
What are the symptoms of coronavirus?
The symptoms often start in the back of the throat with a sore throat and a dry cough.
Other symptoms — fever, shortness of breath, body aches, fatigue and sometimes vomiting and diarrhoea — can signal any number of illnesses, from flu to strep to the common cold.
How do you catch it?
The virus is spread through droplets transmitted into the air from coughing or sneezing, which people nearby can take in through their nose, mouth or eyes.
The viral particles in these droplets travel quickly to the back of your nasal passages and to the mucous membranes in the back of your throat, attaching to a particular receptor in cells, beginning there.
What can I do to prevent it?
Good hygiene, regularly washing and thoroughly drying your hands, and other simple steps can help stop the spread, the Ministry of Health says.
These include avoiding close contact with people with cold or flu-like illnesses, and covering coughs and sneezes with disposable tissues or clothing.
Washing hands for at least 20 seconds with water and soap and drying them thoroughly, before eating or handling food, after using the toilet, after coughing, sneezing, blowing your nose or wiping children's noses, or after caring for sick people can help prevent spreading the disease.
How do you treat it?
There is no specific treatment for coronavirus, but medical care can treat most of the symptoms.
This could involve prescribing antiviral medication used to treat influenza or antibiotics used to treat bacterial infections.
"The mask not only protects you from droplets. It also protects you from bringing your hand, which may have virus on it, to your mucus membranes such as your nose and your mouth."
However, the masks are only effective under certain circumstances. If not changed regularly they can become useless, and far less effective when not used with other hygiene precautions.
Meanwhile infectious diseases expert Dr Siouxsie Wiles told the Herald that culturally in countries like China, people wear masks not to prevent infection, but when they have cold – to stop spreading it.
"It's not very good at blocking viruses coming in. People don't wear them properly, they don't make a good fit around [your face]. If you have a gap, you're breathing stuff in.
"There are other masks that we would use in the lab for when we're doing dangerous stuff and they are very different."
Can coronavirus spread in NZ as it has done in China?
"We don't have the density, so I don't see us having an outbreak as China has," Wiles said.
"If it does establish here, I think it would go along the lines of an influenza outbreak, where a lot of people end up getting it but it's not that serious for everybody – but it may be for some who have underlying problems."
What is a pandemic?
Rebecca S.B. Fischer, an assistant professor of epidemiology at Texas A&M University says three important words are being mixed up: outbreak, epidemic and pandemic.
Simply put, the difference between these three scenarios of disease spread is a matter of scale.
An outbreak is small, but unusual. An epidemic is bigger and spreading. A pandemic is international and out of control.
What else is the New Zealand Government doing to manage the situation?
The Ministry of Health's Pandemic Influenza Technical Advisory Group (the PITAG) brings together 11 of the country's foremost experts on public health and infectious disease.
Now meeting daily, the group has advised the ministry on crucial decisions such as travel bans.
Authorities are also looking very closely at other countries that had managed to control the outbreak - such as Taiwan and Singapore - to see what they're doing right.
Tools like school shutdowns that would normally be used later in a pandemic could be used "preemptively" to help stamp out or slow the spread of Covid-19.