Many of them are linked to big events, described as "a mixing bowl for infection" by the Ministry of Health.
There are two weddings, a stag do, a St Patrick's Day party, an Air Force rugby tournament and a cattle conference that attracted people from 18 countries.
A third are where some of our most vulnerable live — rest homes — killing 14 residents, two-thirds of the country's total death toll.
One came from a cruise ship, where thousands of passengers — many in their golden years — mixed and mingled for 11 days before being allowed to head home without health checks, risking others within their local networks.
These are New Zealand's 16 significant coronavirus clusters. The Ministry of Health said yesterday that three were declared closed because there was no longer transmission of the virus associated with the cluster.
Seventeen of the country's 20 deaths have been linked to a cluster. And they do not discriminate by area, with cases in Auckland and down to Bluff. Eleven are in the North Island and five in the South Island. Ten have been caused by overseas exposure. The source of six is unknown.
There are more clusters around New Zealand but the ministry only publicly reports those with more than 10 cases. Defined as being connected through transmission and including people who are not all part of the same household, the number of significant clusters has grown despite our being in lockdown and borders being closed to non-residents.
1. Bluff wedding — 98 cases, 2 deaths
The bride and groom considered postponing their wedding as concerns over Covid-19 grew. Some guests decided not to attend.
But as the groom's father could not make a later date, they decided to go ahead on March 21.
Seventy guests travelled from around the country to attend, greeting each other with elbow touches and waves at the ceremony in Invercargill, where the couple live, before the party moved on to the reception in Bluff. It was at Oyster Cove Restaurant and Bar, a popular venue overlooking the sea at Stirling Pt.
One guest was an Air New Zealand steward who had returned from the United States days before. He is believed to have been asymptomatic.
The newlyweds had a gathering of family and guests the next day and the steward was said to be coughing.
Four days later, the couple learned of the outbreak when a guest told them they had tested positive for Covid-19.
The groom's father, Chrysanths (Christo) Tzanoudakis, 87, fell ill and was later admitted to Wellington Hospital. He died on April 10.
The newlyweds also became ill, as did staff at the bride's workplace, the Invercargill City Council. On April 21, one employee's husband, Alister Peter Brookland, known as Barney, died at his Invercargill home.
2. Marist College — 94 cases
In mid-March, a teacher at the Catholic girls' college in the Auckland suburb of Mt Albert was off work with symptoms similar to coronavirus.
Events had been held at the school recently — a Fiafia night on March 14, and an extended whānau meeting on March 18. The teacher was swabbed on March 19. On March 22, the teacher's case was confirmed and the school was closed.
At that stage, all of New Zealand's cases had been linked to overseas travel but the teacher hadn't been overseas, or in contact with anyone who had recently returned home. A few days later, the Prime Minister announced all schools were to close anyway.
More and more people contracted the disease including students, staff and parents. Principal Raechelle Taulu also got it.
3. St Patrick's Day event — 76 cases, 1 death
The advertisement for the March 17 party at Matamata's Redoubt Bar and eatery said "Let's get sham rocked!" with green beer, a jig off, a band, and festive staff.
A couple of days later, a staff member became sick. By March 29, Matamata had nine confirmed cases and was added to the list of clusters.
On April 2, Dr Kevin Snee, Waikato DHB chief executive, said they were no longer solely focusing on the event: "It appears there was also some transmission at that site during the surrounding days as well."
• Covid19.govt.nz: The Government's official Covid-19 advisory website
Days later, Denis Albert Moore, 94, of Matamata, a British World War II veteran, became unwell. He was eventually taken to hospital where he died from the disease on April 16. He is believed to have got the virus from a relative who works at a different hospitality venue in town.
4. Rosewood Rest Home — 55 cases, 11 deaths
The first case at the Christchurch rest home was confirmed on April 3. Given strict visiting restrictions under lockdown, Canterbury DHB believe a staff member brought the disease in.
By April 9, the cluster had its first death, a woman in her 90s.
5. Auckland stag party — 39 cases
Before the March 26 lockdown, a stag party was held in Auckland. It became a cluster, with people who were at the function passing on the disease within their household bubbles.
6. World Hereford conference — 38 cases
About 120 people from 18 countries descended on New Zealand for the conference on March 4.
They did a quick tour through the North Island before joining the conference in Queenstown, which went for four days from March 10.
It was attended by 400 delegates and at that time New Zealand only had two or three cases. The programme included presentations at the Millennium Hotel, a gala dinner, visits to various Hereford farms and the Wanaka A&P Show, which was attended by 40,000 people.
After the conference, NZ Hereford Association president Colin Corney took a group on a tour through the lower South Island. On March 17, he got a phone call from a colleague in Australia to say a person who'd been at the conference had tested positive.
"I had four coaches, about 150-odd people. So I parked everyone up in a wool shed, no one was allowed to leave until I got some advice."
He rang the helpline and was advised to drive to the conference members' accommodation. Health officials called him back and said it was unlikely the person was in a contagious state during the time they were at the conference.
After returning from the tour, Corney had a meeting with his general manager and the ministry, who said the risk was low, so they went for a coach tour around Christchurch.
7. CHT St Margaret's Hospital and Rest Home — 35 cases, 3 deaths
Early in April, the Te Atatū rest home confirmed its first positive Covid-19 result. CHT Healthcare Trust chief executive Max Robins has said it's unclear how the virus got into St Margaret's.
To help with the staffing shortage, on the weekend of April 17, 20 residents were taken to Waitākere Hospital.
Three residents have died — a woman in her 70s on April 20, a woman in her 70s on April 24, and a woman in her 90s on April 26.
8. West Auckland — 30 cases
A cluster is believed to have started in the West Auckland community in March.
Five of the cases involve staff members at Spectrum Care, an Auckland facility caring for people with intellectual disabilities.
They are believed to have contracted the disease in the community and not at work.
The centre was already closed at that point and no clients have been affected. The remaining cases are within the community.
9. Ruby Princess cruise ship — 24 cases
The ship set off from Sydney on March 8 with guests eating together in the dining hall and at buffets, sharing the pools and sitting side-by-side at onboard shows. An infected waiter or someone who handles food is likely to have spread coronavirus.
The ship visited Fiordland, Dunedin, Akaroa and Wellington before reaching its final destination of Napier on March 15. It cut short its final leg as New Zealand announced the travel ban, arriving back in Sydney on March 19.
About a dozen passengers reported feeling unwell and had swabs taken for Covid-19. But almost 2700 passengers were allowed to leave the ship, catching trains, buses and overseas flights to get home.
Napier couple Andrew and June Ranyard — among 56 New Zealanders on board — would later say they had no clue there was an outbreak on board the ship when they disembarked and flew home.
They started to experience coronavirus symptoms the next day.
At least 18 passengers from the ship have died and hundreds of confirmed cases in Australia have been linked to the vessel.
Twenty-two people in New Zealand have tested positive, including residents at Gladys Mary Care Home in Napier. New South Wales police announced a criminal investigation into the ship's operator, Carnival Australia, while lawyers have mounted a class action. New Zealand is also exploring legal action.
10. George Manning Lifecare and Village — 20 cases
On April 2, a resident of the Christchurch rest home tested positive. The village eventually had four confirmed cases — two residents and two staff — and 15 probable cases (their tests had come back negative but they showed symptoms early on).
11. Group travel to New York — 16 cases
A group of mostly middle-aged Wellington friends who travelled together on a trip to New York are among the significant clusters.
The cluster was declared closed yesterday.
12. Air Force rugby team — 16 cases
The RNZAF men's and women's rugby teams attended the Anzus Shield rugby tournament in Denver, Colorado, on March 12 with teams from Australia and the United States.
The competition was cancelled after three days due to the global spread of Covid-19.
A spokeswoman says none of the team's positive cases required hospital care and all had been self-isolating at various Defence Force locations and private residences.
The cluster was declared closed yesterday.
13. Atawhai Assisi Rest Home & Hospital — 15 cases
On March 10, a nurse visiting from Australia went to see her father at the rest home on the outskirts of Hamilton. She tested positive for the disease when she returned home.
Her father showed no symptoms but was tested because of his contact with his daughter. On March 22, his test showed he was positive.
Several staff also tested positive.
14. Ellerslie Gardens Lifecare — 13 cases
A nurse returned from Zimbabwe on March 10 and — due to there being no travel restrictions or self-isolation rules in place — returned to work at the Auckland rest home on March 15 for her night shift. She tested positive for the disease on March 21.
15. Wellington wedding — 13 cases
The wedding was held on March 14, at Boomrock Lodge, on 650ha of farmland in Ohariu Valley. It is understood a guest, who was unaware she was infected, had travelled abroad.
The cluster was declared closed on April 25.
16. Living Earth — 10 cases
A team member at the Christchurch compost company tested positive for the disease on March 22. The person contracted the virus after being exposed to an international tourist on March 12, who tested positive when they returned home. Living Earth's owner, Waste Management, has said only four of the cases are team members at the company.
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They allege the Crown ignored Treaty obligations by not engaging with them.