Further tests are being carried out this week to confirm if highly pathogenic avian influenza (HPAI) has been contained to one Otago egg farm.
The H7N6 strain of the virus was discovered at Mainland Poultry's Hillgrove farm near Moeraki in late November.
It prompted a rigourous biosecurity response that shut down the farm, ran extensive testing for the virus at the site and other linked farms, and culled the entire flock of 200,000 birds across its four sheds.
Ministry for Primary Industries' (MPI) chief veterinary officer Dr Mary van Andel said cleaning and thorough disinfection were underway and would continue at the site over the next several weeks to ensure all traces of the disease were removed.
But she said there was some optimism around how far it had spread.
"We remain confident that we are on the right track to stamping out H7N6, but there is still work to do," van Andel said.
"We are continuing our rigourous testing of samples due to the disease's incubation period and ongoing surveillance and there remains no signs of HPAI outside of Mainland Poultry's farm at Hillgrove."
MPI will work with the company in regards to an appropriate standdown period once decontamination was complete, she said.
Egg Producers' Federation executive director Michael Brooks said testing at the Hillgrove site and other farms connected to the site had returned negative results to this point, suggesting it could be a "one-off situation."
"It just appears to be an extraordinary coincidence that it happened at the same time as there's been heightened concern about the H5N1 strain," Brooks said
Officials had warned the sector to prepare for the possible arrival of the H5N1 strain of the viral disease that was circulating the globe for months before the outbreak.
Brooks said the sector would not sit on its laurels because the threat of the more infectious and fatal H5N1 strain remained.
"While it's been very distressing for the farm concern and frightening for the industry, it is pleasing that the work that's gone in has seen it restricted to one site only.
"It's taught MPI and the industry a lot about the specifics of avian influenza, even though it's not the H5 strain, it's still taught us a lot.
"So if if you could say there's a silver lining, I guess the silver lining is that it will help us in the preparation for H5N1 if and when that arrives in New Zealand."
Brooks said MPI and the sector would hold a "major debrief" about the lessons learned during the biosecurity response after Christmas.
MPI has revoked a restricted place notice it placed on a free range layer farm in Dunedin in the week following the first discovery when dead birds were found on site.
But MPI said these birds tested positive for endemic chronic fowl cholera, not avian influenza.
Van Andel said MPI was making positive progress in resuming safe trade, after the discovery halted some exports - though some have since returned to Australia.
"We're in close contact with relevant trade partners. To date, we've reached agreement with Australia to continue the export of some poultry products including chicken meat, dried pet food, and dog rolls that meet avian influenza heat treatment requirements, worth more than $50 million," she said.
"It's important to note that while there are common elements across markets, solutions are agreed with each country. Work to resume New Zealand's exports of day-old chicks and hatching eggs continues."
