With borders open and holidaying New Zealanders returning home, Covid cases have jumped and more than half of them are the more infectious new sub-variants, says epidemiologist Professor Michael Baker.

The Ministry of Health says there are 6223 new community cases and a further 22 Covid-related deaths today.

The 22 deaths occurred during the past four days.

There are 733 people in hospital with the virus, including 16 in intensive care.

The ministry said it was "closely monitoring" the continued increase in positive cases and hospitalisations as part of an "ongoing review and updating the response to the current community outbreak".

Today's reported deaths take the total number of publicly reported deaths with Covid-19 to 1827.

Of the people whose deaths were reported today, five were from the Auckland region, two were from Waikato, one was from Lakes, two were from Hawke's Bay, one from Taranaki, three from Whanganui, two from MidCentral, one from the Wellington region, three from Canterbury/West Coast, and two from Southern.

Two of the people who died were in their 40s, one in their 50s, one in their 60s, five were in their 70s, eight were in their 80s and five were aged over 90.

Of these people, 10 were women and 12 were men.

In today's statement, the ministry said the case, death and hospitalisation numbers "emphasise the importance of everybody doing the basics well" to help prevent infection and serious illness.

"In particular, people should stay home if they are unwell, take a rapid antigen test (RAT) and upload the result on My Covid Record, and isolate if positive or while still symptomatic," it said.

The seven-day rolling average of community case numbers today is 9803.

The weekly Covid-19 hospitalisations seven-day rolling average is 737. This time last week it was 554.

The average age of current hospitalisations with the virus is 64, while cases in ICU or HDU number 16, the ministry said.

The cases in hospital are in the following districts: Northland (25); Waitematā (126); Counties Manukau (51); Auckland (86); Waikato (56); Bay of Plenty (38); Lakes (21); Hawke's Bay (34); MidCentral (31); Whanganui (18); Taranaki (13); Tairawhiti (7); Wairarapa (10); Capital & Coast/Hutt (56); Nelson Marlborough (9); Canterbury/West Coast (119); South Canterbury (11); and Southern (22).

The number of new cases that have recently travelled overseas is 270.

The number of active total cases, meanwhile, is 70,762. These are cases identified in the past seven days and are not yet classified as recovered.

Throughout the entire pandemic, the total number of confirmed cases in New Zealand is now approaching 1.5 million.

Some 1,490,606 people in Aotearoa are confirmed to have caught the virus.

Border cases jump

"The number of cases detected at the border jumped from 10 a day in early March and then in June it jumped and we hit 100," Baker said.

"Since then it has really shot up and hit 300 in early July. It is going up rapidly at the moment."

Baker said the driver for the higher numbers was the increase in people coming in - and also Omicron was surging in source countries and in New Zealand.

"As soon as we changed our system from MIQ to home isolation, the numbers of new variants have been rising," Baker said.

"I guess the big message is we are fully connected to the rest of the world and we will see more of these new variants."

Baker said there was no longer a "four-week lag" between cases in Auckland spreading to the rest of New Zealand.

With flights from overseas into all major cities, cases throughout New Zealand were more even.

Baker said half of the cases were from Australia but noted New Zealand was now "properly connected with the diversity of these viruses from around the world."

He advised New Zealanders with an overseas trip booked to make sure they were fully vaccinated with any boosters available to them.

"A lot of travellers will be in older age groups, so the booster strengthens immunity, cellular immunity and antibodies.

"It gives you some protection from infection but also protects you from serious outcomes."

He said mask use was still the best line of defence for the airborne disease.

"People should be wearing a mask anywhere indoors."

RNZ reports, meanwhile, that GPs are concerned antiviral treatments for Covid-19 could cause reactions in patients with comorbidities.

From tomorrow, the access criteria for three antiviral treatments will include people aged 75 years and over and those who already have been in intensive care because of the virus.

General Practice Owners Association chair Tim Malloy told RNZ that although the intention was good, there were real risks associated with the treatments.

"Our biggest worry in primary care is of course that that could generate even more work."

Another risk was that some of the antivirals' formula could interact poorly with other common medications, he said.

It was important patients with comorbidities didn't change their current treatments in order to take the antivirals, Malloy said.

Malloy was concerned it could lead to more people needing hospital treatment.

On Saturday, 29 more people were recorded as having died with Covid in New Zealand, and there were 9241 community cases reported.

There were 761 people in hospital with Covid including 15 in intensive care and all 29 people died in the past 29 days.

The seven-day rolling average of community case numbers on Saturday was 9984. The previous Saturday, it was 8687.

The seven-day rolling average of deaths was recorded as 20, and there had been 1805 publicly reported deaths. The seven-day rolling average of hospitalisations was 727 - it was 520 a week ago.

Of the people whose deaths were reported on Saturday, three were from Auckland, four from Waikato, two from Bay of Plenty, three from Lakes, two from Hawke's Bay, two from MidCentral, two from Wellington region, three from Nelson Marlborough, four from Canterbury/West Coast and four from Southern.

Two were in their 60s, three in their 70s, 16 in their 80s and eight were aged over 90. Nineteen were women and 10 were men.

The Ministry said the number of deaths announced each day may fluctuate due to routine delays in reporting. Saturday's increase in reported deaths since yesterday reflected that delay - it included eight people who died on July 14 and 11 who died on July 15.

From Monday, access to three antiviral treatments for Covid will be widened to include those aged over 75 and those who had previously been to ICU as a result of Covid.

GPs could prescribe Paxlovid, Lagevrio, and Veklury to those people - including providing a "back pocket prescription" people could have ready in case they tested positive for Covid at a later date.

The Ministry also issued a reminder that people should wear masks to help stop the spread of Covid, saying it was one of the best measures to reduce the transmission of infectious respiratory illnesses.

"Even if you're fully vaccinated, or have had Covid-19, continuing to wear a face mask is important in keeping you, your whānau, and your community safe.

"As a general rule, the Ministry urges people to wear a mask in public indoor settings outside the home and in poorly ventilated spaces, or when it is hard to physically distance from other people."

Masks must be worn on public transport, at transport hubs like airports and bus stations, inside public venues like museums and libraries, when visiting healthcare services, and in retail businesses.

Masking was particularly important around more vulnerable people, especially those in aged care.