Much of New Zealand is one or two weeks behind Auckland's Covid-19 curve, and the country might experience two peaks of hospitalisations, a data modeller says.
University of Canterbury mathematics professor Michael Plank told Morning Report because some people were not logging their rapid antigen test results, it was hard to tell the trend in actual case numbers.
"Case numbers have been pretty difficult to interpret since the introduction to RATs. The hospital numbers are more reliable but it's important to remember they are also more lagged because of the time it takes for someone to get sick."
Hospital numbers typically lagged behind cases by about a week, he said.
Yesterday there were 17,522 new cases of Covid-19 in the community and 696 people in hospital.
At Auckland's Middlemore Hospital, doctors were stepping in to cover nursing shifts as staff absences reach a critical point.
There were 195 people in Middlemore with Covid-19 yesterday and 520 across Auckland's three main cities.
Auckland City Hospital postponed more elective operations as the number of Covid-19 patients kept rising.
Yesterday there were 189 people with the virus in the hospital.
The hospital had four tiers of priority for planned operations and was now mostly doing only the highest, plus some of the next level down where it could.
It was also cutting many outpatient appointments.
The changes freed up space for Covid-19 patients and were to help ensure there were the staff to look after them, as a growing number of frontline workers isolated because of the virus.
All of Auckland's hospitals have scaled back planned operations, and all elective surgery centres are either fully or partly shut down.
They were still doing acute or emergency surgery.
In Auckland, the next seven to 10 days were a critical point in the outbreak and would be tough going on the health sector, many working in the sector believed.
Plank said models suggested hospitalisation would most likely peak nationally at around 1000 people.
"It's a bit more complicated than that because of the Auckland versus the rest of the country, we could sort of see two peaks, one driven by the Auckland cases and another one as it spreads to other parts of the country," he said.
Hospitalisations were likely to peak in two to three weeks time in Auckland, he said.
Wellington and Christchurch were about one to two weeks behind this, he said.
"If we do start to see increasing cases in older age groups or in unvaccinated groups then that's a warning sign that there could be incoming hospitalisations coming in the next few weeks or days."
Unvaccinated people made up a high number of the hospitalisations, he said.
The Ministry of Health was urging people to self-report rapid antigen test results, whether negative or positive and regardless of whether someone in the household had already reported theirs.
It says self-reporting of RATs helped to provide a clearer picture of how the pandemic was progressing.