Cases were doubling every three to four days and were expected to peak in around six weeks' time.
Countdown supermarkets have been planning for the expected larger-scale outbreak.
Staff at distribution centres and e-stores have been using rapid antigen tests before shifts and there were plans in place to close select stores to consolidate staff.
"Rapid Antigen Tests are playing a critical role in managing the impact of Omicron on food supply and we're already using them in our distribution centres and e-stores when our teams start their shifts," said Kiri Hannifin, Countdown's general manager of quality, safety and sustainability.
"We expect to see increased levels of teams off work as Omicron spreads in Aotearoa and we may need to temporarily close certain departments in our stores over the coming weeks as we move teams to support critical areas like checkouts or online shopping, or into other stores."
Hannifin said there had been a lot of contingency planning to ensure teams could quickly adapt so the essentials were still available.
"We've also been actively expanding our network capacity and investing in additional infrastructure, such as the Penrose e-store, to ensure we can continue to provide Kiwis with a reliable online shopping service."
Priority Assistance service was also available for the most vulnerable who could not leave their home during an outbreak.
People with chronic illness, the elderly, heavily pregnant, self-isolating, and people with a disability that makes it difficult to shop in-store are given priority.
Grocery alternatives like The Honest Grocer, Supie and Ooooby also offer online ordering and delivery. Photo / Supplied
Emma Wooster, corporate affairs manager at Foodstuffs NZ, which owns Pak'nSave and New World supermarkets, said demand for online was growing but there was plenty of availability.
"We've ramped up online before and we're ready to do this again if we need to," she said. "We currently have plenty of capacity."
Plans were in place to deal with demand and also staff shortages - including reducing hours and store closures.
"All Foodstuffs stores have remained open throughout the pandemic, however, reducing opening hours to give teams time and space to get products on the shelf is something our owner-operators can choose to do," Wooster said.
"All our stores are owner-operated so these decisions are made locally and only if needed - we are ready."
Mum gives her top tips
An Auckland family of five, at the tail end of a 25-day isolation period, said careful and considered online shopping was essential.
The family started isolating on January 30th when their teenage son tested positive, they think after visiting shops when Soundsplash attendees returned to Auckland.
As the final person to test positive, the father is still isolating and is hoping to return a negative test tomorrow.
The woman said people should make a plan for if/when they need to self-isolate - especially with food and personal essentials.
"My biggest tip would be to stock up now if you can afford to, on ingredients for basic meals that can be cooked by a family member who doesn't usually cook."
The woman said family members were sick at different times and sometimes the children prepared meals.
"Freeze some bread and milk, have plenty of tissues, toilet paper, sanitary items you would normally buy regularly."
The Auckland-based family was able to shop online but said there were times delivery slots were scarce and deliveries were late because drivers had called in sick.
"Meal planning is a great idea so you don't waste money buying random ingredients you can't put together into a meal."
She said the best pick-me-up was friends who visited their driveway in silly costumes to drop off treats.
