Health authorities are scrambling to contact 100 passengers on board two domestic flights after a second New Zealander was confirmed to be infected with coronavirus.
It emerged yesterday the infected Kiwi woman in her 30s had also taken an international flight and visited two medical centres after feeling unwell.
Her family is now in isolation and two Auckland high schools are on alert for the virus, with officials calling for calm last night after the family had been subjected to "sustained and abusive bullying" on social media.
Director-General of Health Ashley Bloomfield told media the woman had returned to Auckland from a holiday in northern Italy via Singapore on February 25.
On Monday, the woman flew from Auckland to Palmerston North on Air NZ flight NZ5103, returning on the same day on Air NZ flight NZ 8114.
The Herald understands the woman travelled to Palmerston North for work but returned to Auckland after becoming too ill.
An Air New Zealand spokeswoman told the Herald NZ5103 had 60 passengers onboard and NZ8114 had 41.
Bloomfield said everyone on these flights was being contacted by authorities and were advised to call Healthline on 0800 358 5453 if they had any symptoms.
But he stressed that the chance of anyone being infected other those who had been in close contact with the woman was "very low".
One "terrified" 79-year-old grandmother who was on a domestic flight with the infected woman contacted health officials herself and was told someone would be in touch within 48 hours, her granddaughter told the Herald.
The elderly passenger only learned yesterday afternoon that the Palmerston North-Auckland flight on March 2 included the woman who had tested positive for coronavirus on Tuesday night.
"She was very scared about the whole thing anyway but now she's terrified," her granddaughter said.
The 79-year-old was now worried that she might have been exposed to the virus and was frustrated health officials hadn't been in touch sooner.
Meanwhile, Softball World Cup staff also shared a domestic flight with the female traveller.
The under-18 men's softball World Cup was held in Palmerston North and two Kiwi tournament representatives were on the March 2 flight to Auckland.
They were not showing any symptoms, did not feel unwell and had registered with the Ministry of Health's coronavirus helpline. The pair had been told they didn't need to self-isolate at this time.
Bloomfield told media the infected woman had no symptoms when she returned from northern Italy, but felt unwell in the following days.
She went to two medical centres, and a swab test taken on Monday was confirmed as Covid-19 at 6pm on Tuesday evening.
Health officials immediately notified her and her family and started tracing people who were potentially in close contact.
Auckland Regional Public Health Service director Dr William Rainger says the family has done everything right and has minimised the risk to others.
Yet they have become the focus of sustained and abusive bullying on social media and are being hounded by the media.
"There is a high level of anxiety and concern in the school and wider communities, but it is not acceptable to attack people who have been caught up in this global outbreak.
"They have taken all the right actions to protect others."
Rainger said the public health service was worried that such attacks would lead people to hide any illness that might be COVID-19, and not seek medical attention.
"We will not be able to contain this spread of this illness, if the public response is so hostile towards cases and their families," he said.
Bloomfield said the Ministry of Health backed the ARPHS message.
"I want to say that this is a Kiwi family that has been affected by a virus that is part of a worldwide outbreak. What they need is support and understanding.
"Our task is to ensure they have all the support and health care they need."
The woman's partner, who also travelled to northern Italy, had been feeling sick and was awaiting test results last night.
The World Health Organisation said the number of people who don't have symptoms of Covid-19 but infect others is unclear but appears to be relatively rare.
Bloomfield stressed that the chance of a widespread community outbreak remained low and there was a "very low" chance that the woman had infected anyone outside of people she had been in close contact with.
"However there are what we call casual contacts, so it's not zero. Therefore it's important those people are aware of the situation and are able to respond very quickly if they do develop symptoms and call Healthline."
Airports and aircraft also had regular, rigid cleaning routines.
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The family, including two high school children who didn't go to Northern Italy and weren't showing any symptoms, were in self-isolated in their home.
Their high schools - Westlake Boys and Westlake Girls - had been alerted but not closed.
A letter from the Auckland Regional Public Health Service to parents who have children at Westlake Boys and Westlake Girls said:
"This disease is managed the same way as other infectious diseases, like mumps, where people who are close contacts – but do not have the disease – are kept away from others, in case they become contagious.
"There will be high levels of anxiety amongst parents and students, and there will be commentary in social and other media.
"Please understand that people are not considered at risk if they have been close to a contact – as the contact does not have the disease. Contacts of contacts do not have to take any action such as isolating themselves," the letter says.
Officials were talking to the woman and her partner about where they have been and what they'd been doing since returning to New Zealand, Bloomfield said.
"The Auckland Regional Public Health Service gets a day-by-day, movement-by-movement description and then does an assessment about whether there is potential for close contact."
Prime Minister Jacinda Ardern said the Government was trying to stay ahead of the coronavirus challenge.
She said people had a role to play as well by having good hygiene, staying home when unwell, making sure to wash hands properly and catching their coughs.
"Those are all things that do make a difference.
"We are equipped to deal with these situations. We have a plan that is being operationalised."
The virus is understood to spread through droplets from coughing and sneezing.