A leading epidemiologist says it appears the country is experiencing a fifth wave of Covid-19.

Te Whatu Ora is reporting more than 5800 confirmed cases of Covid-19 this week, and more than 200 hospitalisations.

“It is the highest hospitalisation figure in six months, the highest wastewater detection rate since January," says Professor Michael Baker.

"The real number of cases would be higher than what is being reported too.

"Part of it is the change, the removal of the requirement for self-isolation and also the end of the leave support scheme back in mid-August. We see case numbers and self-reported numbers dropping off.”

Professor Baker says testing of wasterwater is an indicator of the rise in Covid-19 cases.

"But the thing to look at now, of course, is the wastewater testing and this doesn't depend on human behaviour, this is showing a really big uptick in detections of the virus across the country at the moment.

"We have to go back right back to January to see this number of copies of the virus in the wastewater across New Zealand. So that's one thing to look at, and the other is the hospitalisations - and they're at their highest point for six months.”

"So we're very much having this fifth wave of infection at the moment."

Professor Baker says with mandatory self-isolation periods and work subsidies largely removed, people may be feeling more inclined to go to work with Covid.

He suspected many Kiwis were not aware they could get a booster to strengthen their protection against the virus, which had killed nearly 3500 New Zealanders already.

"That's really critical… that's been freely available for everyone, 30 years of age and over from early this year. Unfortunately, only about 50 per cent of adults have actually had their fourth dose and so they're really missing out on this protection - so that would be a really important thing for people to check up on."

Te Whatu Ora data showed that as of last week, fewer than 1 million fourth doses had been given. Only 4000 doses were delivered in the week to November 3 in total - including first-timers and people under 30, despite hundreds of thousands being eligible and the vaccine being free.

There was no single variant dominating at present. EG.5 - also known as 'Eris' - accounted for about half of all cases in late October after first emerging mid-year, but was "not particularly remarkable", says Professor Baker.

Instead, he blames the surge on "waning immunity".

"People are more vulnerable and that's driving another wave, and it looks like this is the way the virus is going to behave for the foreseeable future - with peaks and troughs - and we're very much in a peak at the moment."

He says the best protections remained to stay home if sick, wear a mask in poorly ventilated areas and get a vaccination booster.

"Stay home if you're sick… you're also protecting the people from other viruses that you might have like influenza or RSV."

And assume that if you're in a room with "more than a handful of people, there's a reasonable chance that someone else will be infected with the virus".

- RNZ