By Katie Todd of RNZ.
At least two people who have tested positive for Covid-19 went to the Wanaka A&P show this month.
The show on 13 March was an optional stop-off for about 300 guests from the World Hereford Conference in Queenstown, four of them have now tested positive for the virus.
Conference delegates came from New Zealand, Australia, Europe, South Africa, North and South America and visited the Millennium Hotel in Queenstown and two central Otago stations, as well as the A&P show.
Health authorities have been trying to trace all of them, since confirming the cases yesterday, but say there is a low risk of close contact for about 40,000 other A&P show guests, meaning they do not have to self-isolate if they do not have any symptoms.
Wanaka A&P show event manager Jane Stalker said the Southern District Health Board had advised other people who attended the show were "casual contacts", with a low risk of close contact to anyone carrying the virus.
"For all 'casual contact' situations, the Ministry of Health and SDHB [Southern District Health Board] are reminding people to follow the guidance of washing hands, maintaining social distancing and if people develop symptoms, they should self-isolate and call Healthline," she said.
President of the Hereford Association, Colin Corney, said he was confident all the conference delegates could be contacted and alerted to the confirmed cases.
"We have been able to contact them via email and other different means," he said.
Those in New Zealand were being asked to self-isolate.
However, Stalker said the ministry was yet to get in touch with A&P show staff for contact tracing.
• If you have symptoms of the coronavirus, call the NZ Covid-19 Healthline on 0800 358 5453 (+64 9 358 5453 for international SIMs).