"For every case that's recorded we might have another five people out there who have very mild symptoms that are not being tested.
He said a delay in recording infections would also skew the numbers.
"When the curve is rising very rapidly it's still telling us about infections that happened maybe a week ago, it's always looking back in time because people who are exposed and incubating an infection take a median of three days, and then a few more days to get sick enough to go and get tested and then the result has to come through.
"And when you put both those factors together, the true number of infections in the community is probably an order of magnitude higher than the numbers we're seeing in the data account ... about 10-fold higher."
He said a move to phase 2 of the government's Omicron management plan, unveiled last month, was imminent.
"We don't actually have a lot of choice, unfortunately, short of very strong measures that I think people don't regard is proportionate at this stage."
In phase 2 the focus remains on slowing the spread, but also balancing the needs of critical services, businesses and the economy.
The self-isolation period drops from 14 days to 10 for positive cases, and contacts need to stay home for seven days.
Critical workers who are close contacts may not even have to isolate at all, if they return a negative rapid antigen test.
Resources would also be deployed more strategically with the government promising to watch vulnerable communities and those at high risk of severe illness, closely.
University of Otago Associate Dean and immunologist Dianne Sika-Paotonu said evidence and experience clearly demonstrated that Māori and Pacific peoples fell into this camp and it was more important than ever that the government listen to the advice on how best to protect them.
"They need to trust our Māori and Pacific health teams and leaders ... ensuring the work that is being undertaken is appropriate for our communities."
Dr Sika-Paotonu said there was still a lot of work to do to bring up Māori and Pacific tamariki vaccine rates as the virus spread.
"Forty-five per cent of the general [5-11] population have received their first vaccine dose, while for Māori and Pacific the vaccination levels for first doses are at 26 per cent and 36 per cent respectively. So there are inequities that are evident there."
Baker said the Omicron wave would be relatively short, but intense.
"People who are older and have underlying illnesses need to think in the next week or two about cutting down on the social contacts and if they aren't, those are the people making sure they're wearing a high-performing mask.
"When we come out the other side, there'll be much less virus circulating and it will drop away quite rapidly. But that's still many weeks, probably three months away before we do get to that point. So we're going to have to be extra careful of this period to protect the most vulnerable people."
Health Minister Andrew Little has repeatedly said New Zealand is well-placed for an Omicron outbreak - and the ICU and hospital level care capacity is there.
However Nursing Organisation kaiwhakahaere Kerri Nuku said nurses felt differently.
"There's the same sort of emotions that we were feeling almost two years ago, feeling scared, feeling under resourced, under prepared and that people aren't listening to what's actually happening."
She said nurses were in a state of anxious preparation with many told to cancel leave or any plans for professional development until the wave was over.
"It does also make nurses think twice when they go about their own social gatherings, whether or not they should go there whether or not they should go somewhere else ... people are making those conscious decisions about whether to participate in some of the social functions or not.
"It's tense and it's difficult times."
