COVID-19: Case numbers will continue 'going up' as outbreak enters 'growth phase', R-value indicates infections will double every 10-12 days - expert

Anyone with cold or flu-like symptoms should be treating their ills and chills as a possible case of coronavirus, says a COVID-19 data modeller, with 109 new cases detected in the community on Sunday.

Dr Dion O'Neale, a lecturer and modeller at the University of Auckland's Department of Physics, says any symptoms consistent with COVID-19 - including a sore throat, fever, cough or fatigue - should be investigated with a test.

On Monday, 109 new cases of the virus were recorded - the second-highest total since the virus arrived on New Zealand's shores last year. Despite new case numbers typically being lower over the weekend due to decreased testing, O'Neale says this figure is "not surprising", with the number of new infections expected to double every 10 to 12 days. 

"Everything suggests we're well into a growth phase at the moment with this outbreak. We've got a R-value of about 1.3, or a doubling time of around 10 to 12 days, and so we do expect to keep seeing these numbers going up," he told Newshub on Monday. 

"Those numbers are going to continue to grow."

However, the more New Zealanders who are vaccinated, the slower the rate of transmission will become, he says, noting that vaccination is crucial to preventing numbers from getting as high as they otherwise might.

As of Monday, 87 percent of New Zealand's eligible population have received their first dose and 71 percent are fully vaccinated. In Auckland, the epicentre of the outbreak, 90 percent of residents aged 12 and over have had their first jab, and 77 percent have had both doses. 

The stricken region will eventually shift to the 'Red' phase of the Government's new 'traffic light' framework when 90 percent of the populations under Auckland's three DHBs are fully vaccinated. 

But despite the promising progress, O'Neale says other measures need to be implemented to combat transmission. Although 71 percent of eligible New Zealanders have received their second jab, it takes a couple of weeks for the body to develop immunity - meaning not all 71 percent are currently fully protected against the virus. Another nationwide vaccination drive, such as Super Saturday, could "potentially" help to continue boosting uptake, he says, but other measures should not be discounted. 

"[We] need something on top of vaccination as it takes a couple of weeks to develop full immune response after a second dose - even if someone is fully protected, the infection blocking of vaccination is about 70 percent," he told Newshub. 

"We need other measures in place to reduce infections as much as possible."

Despite the significant number of new infections recorded on Monday, hospitalisations saw a welcome drop, decreasing from 50 on Sunday to 35 - all but one of the patients being in Auckland.

O'Neale says the reduction will provide some important "breathing room" for the region's healthcare system as the workforce braces for an influx of patients due to rising case numbers. 

"As case numbers go up, we are going to continue to see more people ending up in hospital as a result," he said. 

He noted the increasing rate of vaccination could help to reduce hospitalisations among COVID-positive patients, as well as the virus shifting into a younger demographic, who are less likely to develop severe symptoms.

With Auckland's senior students only now returning to the classroom after 10 weeks of lockdown restrictions, O'Neale notes that the circulation of typical colds and flus has been significantly compromised due to school shutdowns. As a result, any flu-like symptoms should be treated as a possible case of COVID-19.

"At the moment we haven't had schools go back, so we're not having the spread of usual colds and flus through schools that we'd see. As a consequence of being in alert levels 3 and 4, we really don't have that many other diseases out there circulating - COVID is about the most contagious disease going around at the moment," he says. 

"We'd like to see people treating any kind of symptoms they have as if they are potentially COVID and getting tested. This is particularly true given the high test positivity rates we're seeing in some of those areas in the north of Auckland."