Mask wearing will be “mandatory” in essential stores from tomorrow, as the government announces the new rule to help curb the Covid-19 Delta outbreak.

Masks will be required for everyone over 11 years old in places like supermarkets, bus terminals, and taxis.

Earlier today the Government website on Covid19 said “you legally must wear a face covering” on all public transport, but softened its wording this afternoon to “you need to wear a face-covering on public transport.”

However, it remains clear that if you’re a customer or an employee of a service operating at Alert Level 4, “you legally must wear a face covering.”

University of Canterbury Associate Professor Arindam Basu from the Health & Human Development at the College of Education said “mandatory masking is particularly important now (it was always necessary and many public health scientists have advocated for months!), because of source control.

“The Covid-19 delta variant is particularly problematic for young people (see this report: “Prevalence in those aged 5-49 was 2.5 times higher…compared with those aged 50 years and above”).

He said “there are some unique aspects of this epidemic – few people infect many but most people will not infect anyone. The epidemic spreads via superspreaders, and super spreading is particularly problematic with the delta variant. There is a need to identify the network of people who are connected, so we are probably looking at few cases at this stage, and more people will emerge, possibly in different parts of the country.”

Professor Michael Plank from Te Pūnaha Matatini and University of Canterbury said “at this stage, modelling suggests that somewhere in the range of 50 to 120 people could have been infected prior to yesterday’s positive test result. Many of these will still be in their incubation period so it may take a few days to see them come through in the case numbers.”

He said “there is a wide range of uncertainty in the outbreak size at this stage. If it turns out a close link can be established with a case who has returned from NSW via the MIQ system, the outbreak could be at the small end of the scale. If the source case travelled to NZ from another Australian state not required to go into MIQ, the virus could have been spreading undetected for some time and the outbreak could be much bigger.”

“Genome sequencing results from MIQ are expected later and these will help narrow down the possibilities. Negative wastewater results are a good sign though we need to see results from more recent samples to have confidence.”