Patients in Auckland's cluster are being hospitalised at twice the rate of other Covid-19 cases in New Zealand - and its specific impact on Māori and Pasifika people is likely a major factor.
A Herald analysis found 18 of the 152 cases in the cluster have resulted in hospitalisation - about 12 per cent of cases so far.
Outside the cluster, 5.8 per cent of patients have been hospitalised - 93 out of 1609.
There are still nearly 73 active cases in the cluster, which could mean more patients may require hospital care.
The difference in the need for intensive care unit level (ICU) treatment is even more stark.
So far, five patients from the cluster have needed ICU treatment - compared with 10 other Covid-19 patients.
That meant 3.3 per cent of patients in the cluster have needed ICU treatment, compared with 0.6 per cent for all other cases.
When ICU treatment was considered as a fraction of hospitalisations, 27 per cent of Auckland cluster hospitalisations have required that level of care - compared with only 10 per cent of the rest of New Zealand's Covid-19 hospital cases.
The Ministry of Health is yet to provide a full breakdown of ethnicities of those in the cluster who have been hospitalised.
But it's known that 61 per cent of cases in the cluster are among people of Pacific ethnicities and 21 per cent are among Māori.
Outside the cluster, just 5 per cent of cases have been among Pacific peoples and 8 per cent among Māori.
Today, director general of health Dr Ashley Bloomfield said cases in the latest cluster were comparatively older than cases earlier in the year.
But he added the predominant ethnicities were Māori and Pasifika - groups which tended to have higher rates of pre-existing conditions, and higher hospitalisation rates.
"That will be a major contribution."
University of Otago epidemiologist Professor Nick Wilson agreed the ethnic make-up of the cluster partly explained the extra hospitalisations.
"The first outbreak in New Zealand mostly affected younger returning travellers - the median age group was 20 to 29," he said.
"They had very low levels of chronic conditions, and of course are protected by being young."
It comes after a study by Te Punaha Matatini modellers, published in today's New Zealand Medical Journal, found Māori were 50 per cent more likely to die from Covid-19 than Pākehā.
The researchers singled out factors such as Māori living with more multiple underlying health conditions, and structural disadvantages that lifted hospitalisation rates.
Māori were also at greater risk of exposure because of higher involvement in high-risk occupations and environments and larger social networks.
Study co-author and University of Canterbury mathematician Professor Michael Plank said the trends were "extremely sobering but unfortunately not surprising".
"Covid-19 produces a very wide spectrum of outcomes from very mild symptoms to fatality," he said.
"The evidence now shows that Māori and Pasifika are at higher risk of experiencing more severe illness from Covid-19 right across this spectrum."
Bloomfield said this was one of the key drivers in the ministry's decision-making about responding to the first outbreak earlier this year.
It was a "known issue" and had been identified through the Health and Disability System Review, he said, and the sector was now working to address it.