A leading epidemiologist says isolation requirements should be relaxed when Omicron is surging in New Zealand.

The government is due tomorrow to reveal its phased approach of dealing with Omicron.

Professor Michael Baker said at the moment, we're still treating Omicron like the Delta variant - still contact tracing every case and trying to stamp out transmission to slow down the virus.

That's the right thing to do - for now, he told Morning Report.

"But later on when Omicron is everywhere, it's quite reasonable, in fact it's the right thing to do, is relax the isolation requirements."

At the moment, if you have Covid-19 you isolate for 14 days.

"Internationally we've sent that drop down to 10 days and seven days," he said.

"While the incubation period of Omicron is shorter, around three days, the tail is still reasonably long and there's quite a bit of data coming out that say people still have a big viral load even three or four or five days after their symptoms have peaked."

Seven days would be the shortest isolation should go, he said.

Close contacts currently spend 10 days in isolation. Baker thinks this requirement may drop as well.

"That's still quite a tricky area because you're really looking at the incubation period of infection."

Household contacts of a case need to spend up to ten days in isolation after a case has completed their 14 days, essentially requiring them to isolate for a total of 24 days.

"That's been the requirement throughout, it's just not really noticed that much because in the past the cases would go into an MIQ facility.

This was done to protect family members but things changed when more cases arising in the Delta outbreak meant an increase in people isolating at home.

Baker said countries overseas that are dealing with Omicron outbreaks face a balancing act of stamping down transmission but getting essential workers back to work.

"After all, if a person doesn't have symptoms, they're probably less infectious, they are wearing PPE in the hospital sector and this is what's being done overseas, shortening the isolation period."

Rapid antigen testing 'not the golden chalice'

Lab workers are worried about being overrun when Omicron takes hold in the community.

The Ministry of Health claims labs can handle 62,000 tests a day, but that's disputed by the organisation that represents lab technicians who say we are on the brink of a potential disaster.

New Zealand Institute of Medical Laboratory Science's president Terry Taylor said it is possible to do these numbers for one day but it isn't sustainable.

In the Delta outbreak the labs were able to handle around 30,000 tests without having a major effect on the other diagnostic testing they provide, he said.

"But as soon as we start sweeping up to the 40 to 50 [thousand tests] we're in trouble."

At the moment they can pool PCR samples, increasing the capacity by testing five or six samples together that they suspect will be negative and running it as one sample.

"We know from what we've seen in Sydney that there's going to be around 30 percent positivity rate which means we can no longer do that strategy," he said.

"We are going to be chasing our tail, there's no two ways about it, that's what's happened overseas and we're going to be on the same boat."

Rationing tests is something that may well happen during a surge, he said, and rapid antigen tests will be an important part of the response.

"When we have high levels of the virus circulating in the community the false negative and false positive side of the rapid antigen test doesn't matter so much."

But rapid antigen tests won't keep businesses operating, he said.

"It's not the golden chalice, it's a tool in the toolkit."

Professor Michael Baker said 4.5 million rapid antigen tests won't be enough to regularly screen essential workers to keep operations functioning.

"That's when you need a lot of testing, because you're testing a whole workforce maybe several time a week. So that is a problem.

"We have still got some time, a few weeks before this is going to be a very intense outbreak in New Zealand but we do have to get moving on that."