An investigation has found that COVID-19 transmission at Auckland's Jet Park quarantine facility was likely caused by room doors being opened simultaneously for just seconds at the same time.
Joint head of managed isolation and quarantine (MIQ) Brigadier Rose King released the findings on Tuesday of a probe into the origins of three COVID-19 cases detected in the Jet Park facility between July 27 and July 29.
The Ministry of Health's Deputy Director of Public Health Dr Harriette Carr said the investigation by Auckland Regional Public Health Service (ARPHS) found that while there were no bubble breaches, the three cases were genomically linked to a person in the room opposite.
ARPHS found that doors to rooms on opposite sides of the corridor were opened at the same time for about three to five seconds on four occasions when a COVID-19 case in the room opposite would have been considered infectious.
"The proximity in time and location when doors were open, and likely sharing of air that may have occurred, is considered the most likely explanation for this transmission," said Dr Carr.
"What this investigation has highlighted is how easily COVID-19 can be transmitted, even in tightly controlled environments."
How did non-infected people end up at Jet Park?
A group of five travellers was moved to Jet Park on July 15 after one of the group tested positive for COVID-19 on on their first day of arrival in New Zealand.
The group of five were staying in rooms directly opposite from a solo traveller who was moved to Jet Park a few days later on July 19.
Members of the group of five started testing positive for coronavirus, and it was initially thought they had caught it from the person in their group who had the virus. But genomic testing linked them to the case in the room opposite.
The linked cases did not arrive from the same country, or share flights and they were staying in different managed isolation facilities prior to transfer to Jet Park, so the investigation came to the conclusion that the virus must have travelled across the hallway when doors were opened at the same time.
All of the cases had the Delta variant.
Brigadier King said it's the first time something like this has happened at Jet Park.
"As such, we've made immediate changes to meal delivery and health check procedures to help prevent future episodes of doors opening at the same time," she said.
"There are low numbers in Jet Park currently so we've also been able to separate returnees more widely throughout the facility as much as practicable."
Brigadier King there were elements of human behaviour which make it difficult to control.
"We're not able to control the exact timing of returnees opening their doors - but we've put measures in place to help reduce the chances as much as is practical.
"The MIQ Technical Advisory Group has considered this investigation and is working on recommendations to reduce the number of occurrences of door opening and, where possible, eliminate synchronous door opening across all 31 facilities.
"We've had almost 165,000 people through MIQ and very few incidents of in-facility transmission. Certainly we've not had anything like this before at Jet Park.
"It really does highlight how this virus is continually evolving and how vigilant we all need to continue to be."