New Zealanders were being asked to be honest and thorough in their biosecurity declarations.
O'Connor said the disease had been considered the "doomsday disease".
He referrred to what happened in the UK when hundreds of thousands of animals had to be slaughtered.
O'Connor said $110 million in the recent Budget had gone towards addressing diseases like foot and mouth.
He said with all the efforts put in they hoped not to find foot and mouth in NZ. He said he could not put a figure on the scale of the risk NZ now faced.
There were no direct flights to and from Indonesia, but given Australia's proximity and growing numbers going to Bali, that had heightened the risk.
Every container from Indonesia was being inspected, O'Connor said. Inspection of containers meant there would be someone on site who could look for any risk products.
On travel to Indonesia, Ardern said no direct flights meant there were already steps between the countries to prevent the disease from arriving.
Ardern said she was not aware of plans to reopen direct flights to Indonesia from New Zealand, but if that were to happen the appropriate biosecurity measures would need to be in place.
The foot and mouth disease briefing comes ahead of the final stage of the international borders opening again from Sunday, allowing visitors and students from anywhere in the world to come to New Zealand, and the reopening of maritime borders to cruise ships.
The full reopening of the borders is likely to mean an increase of visitors from Indonesia, which is not a visa waiver country, and where the foot and mouth disease outbreak has caused concern for Australia and New Zealand because of the impact it would have on their economies.
Last week, biosecurity officials began a trial of requiring travellers from Indonesia to step onto special mats with disinfecting chemicals to prevent the virus from coming in on footwear.
PM has full confidence in James Shaw
When questioned on the Green Party co-leadership contest, Ardern said the political rules of each party was a matter for them.
This did not affect the running of the Government and so was for the party itself, she said.
Ardern said there was a significant agenda on climate and she had full confidence in James Shaw.
Her decision to put him in that portfolio was not because they needed a relationship strictly with the Greens, but because Shaw was the "right person for the job".
He had helped the Government make the "most significant" progress in climate action than any other government.
Ardern said she pushed back on any suggestions the Government had not been ambitious, adding Labour had come in with a significant agenda themselves.
This was a highly complex area, and Shaw was a minister who had "added value" having been in the role three years.
Leadership rumbles within the Green Party began after enough party delegates at the AGM voted to reopen nominations for the co-leadership slot held by Shaw, instead of re-electing him.
Ardern has already said Shaw would be kept on as Climate Change Minister if he was not co-leader.
This morning Shaw said he would contest the leadership and was "quietly confident" of securing it again – as yet, nobody has publicly said they will contest it.
Green MP Chlöe Swarbrick has today ruled herself out from running for the party's co-leadership.
Eugenie Sage has said she "strongly supports" Shaw, and Golriz Ghahraman said she would not contest it.
Covid-19
On traffic light settings, Ardern said nothing had changed.
The focus now was getting through winter, and now was not the time to change anything, Ardern said.
On a current jump in hospitalisations, Ardern said there was about a two-week lag, and school holidays could have therefore influenced the reporting of cases.
Wastewater data showed there could be a decline in case numbers, Ardern said.
Hospital discharges also changed a lot over the weekend, so the Government would look closely at the next few days.
Govt keeping open mind on masks, mandates and schools
On masks in schools and a mandate, Ardern said the Government was keeping an open mind.
The response from experts was that the education sector wanted flexibility on how to implement mask policies, including requiring them where necessary, rather than a Government-enforced mandate.
On indoor gatherings and comfort levels, Ardern said they were asking people to follow the rules. Where food and drink was available people were not expected to wear masks.
Three Waters
On LGNZ recommendations on Three Waters and separating wastewater, Ardern said she did not believe it was about carving it off, but a transition.
