The actual number of COVID-related hospitalisations, according to Ashley Bloomfield's estimate

Of the official 742 COVID-related hospitalisations, it's possible that only about 556 - or 75 percent - are actually seeking treatment for the virus, based on previous trends.

Director-General of Health Ashley Bloomfield, under questioning from ACT leader David Seymour, told Parliament's Health Select Committee on Thursday that in the first weeks of the Omicron outbreak in Auckland, about 75 percent of hospital patients there because of COVID-related symptoms. 

"We would expect that proportion to get lower with more virus in the community," Dr Bloomfield said. "For example, 40 percent of people turning up at Middlemore's emergency department at the moment are testing positive for COVID seeking care for other reasons."

The Ministry of Health echoed Dr Bloomfield's comments in an official statement, telling Newshub while it's not clear exactly how many cases are actually in hospital for COVID, estimates suggest it's around three-quarters.

"We are developing a way to collect and report this data. We have one estimate that about three-quarters of reported hospitalisations are due to COVID-19 symptoms and the rest have COVID-19 'incidentally'. This is similar to the proportions reported from a US hospital study published last week.

"In countries like Denmark currently it about 60 percent to 70 percent. The Ministry of Health is also unable to comment on whether hospitalised people have COVID-19 or other symptoms as we do not hold that level of detail about patients.

"There have been several outbreaks in hospital wards, which can contribute to COVID-19 hospitalisation numbers. For some of these cases, they contracted COVID-19 from an exposure in hospital. For this reason, hospitals are now routinely screening all patients being admitted."

Dr Bloomfield said it has been difficult to obtain the data because the reason for a patient's admission to hospital is recorded when they are discharged. 

It comes after COVID-19 Response Minister Chris Hipkins told AM on Thursday the Government did not have data on how many COVID-related patients in hospital were there for virus-related symptoms as opposed to other health issues. 

Hipkins said the Government is keeping a closer eye on the number of cases requiring respiratory assistance or intensive care (ICU). 

"One of the measures that we look at for the degree of severity for hospitalisations is the number who require ventilation or require ICU treatment - we have 19 in ICU as of yesterday," Hipkins told AM. 

"That is a number that's going up but that's one we will follow very, very closely because it does help to give us an indication of the sort of severity that the health system is dealing with."

Dr Bloomfield told the Health Select Committee that modelling suggests the Omicron peak is a week or two away. 

"In the next few days the case numbers will give us an indication of whether the outbreak may have peaked in Auckland and be on its way down in Auckland while other parts of the country peak at different times and that's quite important because the overall country-wide pattern hides variation across the regions."

Dr Bloomfield said the Ministry of Health analyses hospitalisations, the number of positive cases compared to the number of negative cases, as well as wastewater, to understand when the outbreak is peaking.