A large house party that took place at a North Shore property on Saturday despite lockdown restrictions has "all the makings of a super spreader event", says aerosol chemist Dr Joel Rindelaub.
The University of Auckland research fellow says it only takes fleeting contact to transmit Delta.
"When you are in an indoor environment like that there is far less ventilation meaning people are going to be exchanging breath, exchanging aerosols, these are the exact types of particles that the virus will latch on to."
His comments follow footage being uploaded to social media showing at least 50 young people partying till the early hours of this morning at a rural North Shore house.
The footage - which shows partygoers drinking alcohol and gyrating with each other on a table - has been condemned by Aucklanders adhering to strict level 3 Covid-19 lockdown rules.
Rindelaub referenced a case earlier this year at an MIQ facility, when two doors open across the hallway for less than 30 seconds resulted in transmission.
"Dry humping is not a Covid-friendly activity outside your bubble. I can say that with some certainty.
"This has all the makings of a super spreader event, so we just hope there weren't any positive cases at this little shindig," Rindelaub said.
The Herald understands the party took place at a large rental property in Redvale, a rural area north of Albany.
A couple who lives next door say the noise started about 7pm on Saturday, and neighbours are "livid".
"It carried on till about 4 in the morning. It was extremely, extremely upsetting and just inconsiderate," they said.
They can only see the back of the party house from where they are, but were told by another neighbour there were about 50 cars in the driveway.
This is the fifth or sixth big party they've heard at this property in the past year or so, since the tenants moved in.
"From what we know it's five youngsters who rent it," they said.
"They had a big party one time when we came home from a movie, there must have been about 500 people there, and about seven police cars down the road, just out of hand."
The couple phoned both noise control and police about 12.45am but say the noise continued.
Police have confirmed receiving multiple reports about videos of the gathering which are currently being assessed.
The videos posted to Instagram, some of which have subsequently been deleted, are believed to show an apartment packed with young adults drinking, dancing and kissing as the captions acknowledged how "packed" the party was.
It was screen recorded and has been posted widely on social media, with people furious at the lack of distancing.
One of those posting videos from the party is a social media influencer and "fitness model" with tens of thousands of followers.
Auckland mayor Phil Goff has labelled attendees "selfish people choosing to behave like idiots".
Auckland is currently under Covid-19 alert level 3, which means no indoor gatherings.
In a statement, Goff told the Herald anyone attending a party in level 3 was undermining the hard work of Aucklanders to suppress the virus and putting themselves and the wider community at risk.
"After a fantastic Super Saturday that saw record numbers of Aucklanders doing the right thing, it's a shame to see a small minority of selfish people choosing to behave like idiots.
"Parties are exactly the sorts of activities that can lead to a super spreader event.
"But this does not reflect the vast majority of Aucklanders who are continuing to follow the health rules to protect their families and community."
The footage has been condemned on social media.
"These people are reckless and are only thinking of themselves. Not thinking of their parents or grandparents," said one person on Facebook.
"Nah because Auckland hasn't had one of the strictest lockdowns just so some entitled, drunk rich people could dry hump each other."
"What a slap in the face to everyone doing their part, and those just trying to get home. I hate people."
A police spokesperson told the Herald they have received multiple reports through the non-emergency line but would not confirm if they were investigating the reports, as it was too early to know.
"At this stage it appears they are in the 'reporting' phase of the process- as they are only just coming in to us ... which is why I suggested ... Check in with us in the coming days and we can see if we can provide an update."
It is alleged one of the guests at the party used an essential worker exemption to travel from outside of Auckland.
Meanwhile, police have also warned they will take prosecution action against organisers of two anti-lockdown protests "in the coming days".
On Saturday about 2000 people congregated at the Auckland Domain and about 1000 at Kensington Park in Whangārei. No arrests have been made at this time.
"While those in attendance generally conducted themselves in a calm manner and adhered to rules around mask wearing and distancing between smaller separate bubbles, the gathering was by its very nature a significant breach of Covid-19 alert level 3 requirements," Superintendent Shanan Gray said.
"Police confirm that they will be taking prosecution action against a number of individual organisers in the coming days."
New Zealand recorded 51 cases of Covid-19 on Sunday, 47 in Auckland and four in the Waikato.
As of 9am Sunday, 28 of the cases had been linked - 18 of those were household contacts, the Ministry of Health said in its 1pm update.
Another 23 cases are unlinked, with investigations continuing to help find their source.
The four new Waikato cases include two that are known contacts of existing cases - one in Hamilton and one in Raglan. One of these people was already in managed isolation.
The Herald has contacted the Ministry of Business, Innovation and Employment for further comment.