Covid-19 modeller Michael Plank says the level 4 lockdown "will be stopping the virus in its tracks" and although case numbers may continue rising during the next week he is hopeful the numbers will start dropping after that.
Director-General of Health Dr Ashley Bloomfield this afternoon announced 11 new community cases of Covid-19 in the Auckland region bringing New Zealand's total number of cases to 21.
Twelve of the cases are all part of the same Auckland cluster, while eight still being investigated, he said.
Michael Plank from the University of Canterbury Mathematics Department said it now appears that the virus has been spreading undetected in the community for a couple of weeks and during this time it has been spreading rapidly without any control measures in place.
He said the modelling suggests that around 100 people were likely infected during that time.
"One of the few pieces of good news is that the wastewater tests from last week in Auckland have all been negative, but because there's a bit of a time lag between someone getting infected and shedding virus into the wastewater system, I think that rules out having a large outbreak with several hundred, but we could still be looking at around that 100 people infected so far."
This afternoon it was announced that three wastewater tests collected in Auckland on Monday this week returned positive results - one was in Rosedale and one collected at both the Western and Eastern stations.
Plank said the fact that there have been a number of young people who have a large number of contacts have tested positive as well as the number of locations of interest could push the number of people infected to more than 100.
He said it is likely that Auckland's lockdown will last longer than seven days.
However epidemiologist Michael Baker said Covid-19 may not have been spreading in New Zealand as early as initially suggested and it was a very precautionary approach regarding those earlier places of interest.
"It may have been that one of the cases had some symptoms of perhaps a cold or some other illness going back a bit further and that the real focus really is on more from around the 10th of August onwards," Baker said.
Plank said they are still trying to establish how many people were infected before it was known that the virus was spreading.
"So we're sort of putting the jigsaw together to get a sense of the size of the outbreak and so we should expect case numbers to go up over the next few days as the contact tracing and the testing results come in."
Plank said large numbers of cases will not necessarily be indicative of how fast Covid-19 is spreading but rather an indication of how large the outbreak is.
He said the lockdown "will be stopping the virus in its tracks".
"We know alert level 4, the strong restrictions we have, everyone sticking to their bubble, will drastically reduce transmission, but of course we won't expect to see that coming through in the case numbers for another week really."
Plank said case numbers can be expected to go up for the next week or so but after that hopefully the effects of the lockdown will become evident in bringing case numbers down.
He said the fact that New Zealand went into lockdown so quickly gives the best possible chance for getting on top of the outbreak.
"It gives our contact tracers the time they need to do the work because once you get up to 600 cases a day like they're seeing in Sydney, it just becomes impossible for the contact tracing system to really do its job effectively."
Keeping New Zealand's Covid-19 numbers down and its contact tracing system going gives the country every chance of eventually eliminating the virus, he said.
This is an official COVID-19 ALERT.
All of New Zealand is now at Covid-19 alert level 4.
The alert level will be reviewed after 3 days for all areas EXCEPT Auckland & Coromandel Peninsula which is likely to remain at level 4 for an initial period of 7 days.
A community case of Covid-19 has been identified.
Stay at home where possible & follow the Alert Level 4 guidelines. This will stop the spread of COVID-19 and SAVE LIVES.
Everyone is asked to:
Wear a mask and keep a 2 metre distance from others whenever you leave your home.
If you are sick, call your doctor or Healthline on 0800 358 5453 for advice about getting tested.
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Practice good hygiene - wash hands often.
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For more information on Alert Level 4 go to [the government website www.covid19.govt.nz]
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