Cluster ‘could very easily stretch beyond Auckland’
The country’s only cluster may have its roots in the City of Sails but the outbreak ‘‘could very easily stretch beyond the Auckland limits’’, a leading data modelling expert explains.
Professor Shaun Hendy, of Auckland University’s Te Pu¯naha Matatini: The Centre for Complex Systems and Networks, contributed to a modelling paper given to the Ministry of Health this week.
Among the findings was a figure cited by Prime Minister Jacinda Ardern during Monday’s announcement that Auckland and the rest of New Zealand would remain at level 2.5 and 2 respectively.
Ardern referred to the paper’s finding that there was a one in four chance a Covid-19 case could breach Auckland’s boundary, saying it informed the Government’s decision-making process concerning this week’s re-evaluation.
The modelling paper, released to Stuff yesterday, reported the possibility of Covid-19 spread to other regions ‘‘will remain as long as there are active cases in the Auckland cluster combined with near normal rates of inter-regional travel’’.
Hendy said the assessment was made based on estimates of the number of detected and undetected
cases that may be present in the community.
‘‘Put those two things together, we can look at the likelihood that we would get a case outside of Auckland. If you are in the North Island, it is something between 20 to 30 per cent. If you are in the South Island, it is between 5 and 10 per cent, so the chances of finding something outside of Auckland is 1 in 4,’’ Hendy explained.
He believed the figure represented a ‘‘high chance’’ of a case escaping Auckland, with the probability influenced by the travel of people in and out of Auckland – the longer an Aucklander stayed outside the region, the riskier the visit.
‘‘This means that people outside of Auckland do need to be taking precautions and not thinking that this outbreak is something that is confined to Auckland. I think what this shows is everybody needs to be cautious around the country.
‘‘There is a tendency to just think it is confined to Auckland but it could very easily stretch beyond the Auckland limits. Certainly when we look within Auckland, [the cluster has] touched all parts of Auckland. It hasn’t just been confined to just one suburb,’’ Hendy said.
Director-general of health Dr Ashley Bloomfield said the 25 per cent figure was ‘‘essentially an average across the country, with the difference between the North and South islands.
‘‘About a week ago, outside of Auckland [in the North Island], the risk was around 30 to 40 per cent, and in the South Island, somewhere around 10 to 20 per cent, so there was difference.
‘‘In both cases, obviously it is not zero and it will keep declining as days go by when we don’t find cases that have been centred outside of Auckland,’’ Bloomfield said yesterday.
One of the latest sources of concern is focused on Les Mills gym in Takapuna, where almost 100 people were classified as close contacts of a Jet Park Hotel health worker who has tested positive for the virus.
As most people develop symptoms four to six days after exposure, the most likely timeframe any potential cases from Les Mills would show symptoms would occur from September 13 to 16.