Delegates at the World Hereford cattle conference in Queenstown - held from March 9 to 13 - are being contacted after four attendees, including two New Zealanders, an Australian and a person from Uruguay, tested positive for Covid-19.
Attendees at that conference are all considered close contacts and are required to self-isolate for 14 days.
Director-General of Health Ashley Bloomfield said the conference attracted visitors from overseas and New Zealand.
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Teams who went to the conference were being followed up.
The four-yearly conference, which was based in Queenstown, was last held in New Zealand in 1984. It attracted breeders from around the world for the week-long event.
A man in his 60s, who tested positive in Auckland after attending the event, flew from Dunedin to Auckland on Sunday, March 15 on flight NZ674.
Another person in their 60s (gender not listed), also tested positive, but their travel details were not listed.
The other two from the conference who tested positive were an Australian and one from Uruguay, who are not in New Zealand so not included on the overall list of cases.
This meant their travel details have also not been revealed.
Close contacts of the cases, which included all attendees at the conference, were being asked to self-isolate.
"They have also been contacted and required to self-isolate for 14 days."
"Southern District Health Board is doing the tracking and tracing work on this with support from the Ministry of Health."
Organised by the New Zealand Hereford Association, the conference had delegates from Europe, South America, the US, England and Australia, and the biggest contingent of 35 from Uruguay.
In addition to pre and post tours, delegates spent several days in Queenstown listening to speakers and hearing industry reports from the various countries.
A pre-conference tour was held in the North Island and a post-conference tour was held in the South Island.
World Hereford Conference members also visited the Wanaka A&P Show, which ran on March 13 and 14.
About 40,000 people were estimated to have attended the popular Wanaka event which injects at least $11million into the Upper Clutha economy each year.
The Southern DHB is alerting people in a number of locations across New Zealand that they might have come into contact with people who tested positive for Covid-19 this week.
As part of its contact tracing process, public health teams notify the public about the movements of infectious cases to maintain awareness of possible transmission and ensure everyone monitors their own health.
Of the confirmed cases of Covid-19 that attended the World Hereford Conference none are residents of, or currently located, in the Southern region.
In addition to conference attendees, a number of people helped organise the conference who cannot be contacted, as the conference organiser has gone into insolvency.
Those who worked at the conference are considered to be casual contacts and have not been asked to self-isolate but should monitor their health and immediately self-isolate and call Healthline on 0800 358 5453 if they develop symptoms such as a cough, fever, sore throat or difficulty breathing.
New Zealand has 14 new cases of Covid-19, bringing the country's total number of cases to 66.
The country's alert level is still at two, Bloomfield says.
There are five confirmed cases in Auckland, one in Northland, one in Canterbury, two in New Plymouth, two in Waikato including one in Hamilton, one in Tauranga, one in the Coromandel and one in Dunedin.
All are in self-isolation, and close contacts are being identified and followed up.
Eleven of the cases have a history of international travel, while one is a close contact of a confirmed case.
There are four probable cases. All four have previously been reported in the media, Bloomfield told a media conference this afternoon.
Just over 1200 lab tests were carried out yesterday. There have now been more than 6000 tests for the virus.
Two cases announced yesterday were possible cases of community transmission. There has still been no firm link to overseas travel identified.
Bloomfield said he understood people in the areas where those two people lived would be concerned but asked they continue good hygiene practices and maintain social distancing while investigations continued.
Any passengers who disembarked from the Celebrity Solstice and the Ruby Princess in New Zealand have been asked to self-isolate.
The two cruise ships recently visited New Zealand and have now had confirmed cases of Covid-19 on board.
Alert level 2 means Covid-19 is "contained but risk of community transmission growing" and human contact must be further reduced.
Bloomfield had a message for people aged over 70, who have been asked to stay home.
"We know many of you are fit and healthy and living active lives but the older we are, the less able our immune systems are to fight off this virus ... we have seen from overseas that older people are at more risk of serious complications so we are strongly encouraging you - in fact urging you - to be aware of the need to stay at home and not to have contact with others."
Friends and family - especially children - should be asked not to visit, he said.
No patients were in ICU, and none of the new cases were in hospital at this point, Bloomfield said.
People have reported struggling to get through to Healthline. Bloomfield acknowledged it was overloaded and said it was not there to give people general information about the virus.
There was enough capacity if people only used it to ask about their symptoms and get health advice, he said.
New Zealand "may well" need to move to levels 3 and 4 to help stop the health system being overloaded, he said.
Bloomfield said we should still not be testing everyone who just has symptoms - the case definition remains someone having a history of overseas travel or an obvious link to overseas travel, or a history of being in close contact of a probable, confirmed or suspected case, as well as having symptoms.
"It's important we test the right people, not people who are at low risk."
Bloomfield confirmed that a person living in a retirement home in Auckland had caught the virus, as reported yesterday. That person lived alone within the village, so he was not particularly concerned as all the right steps had been followed, he said.
- ODT and NZ Herald