Modbury Cluster: SA Health reconstruction lays bare Covid-19 Delta path through unvaccinated people

Detailed reconstructions of ground zero in SA’s last big Covid cluster have confirmed that certain people are a far greater risk of spreading the bug. See the maps.

The power of Covid-19 vaccinations and using QR codes has been laid bare in an official reconstruction into the state’s latest Delta outbreak.

An SA Health review has ­revealed none of the 22 cases linked to the Modbury cluster, which sparked the state’s third lockdown, were double-vaccinated, while only a third had one dose.

The Communicable Disease Control Branch investigation also found a majority of contacts failed to check in at two major “superspreader” events, while only a handful were vaccinated.

Of the cluster’s 13 infectious men and nine ill women – ranging in age from a two year-old girl to a woman, 87 – 14 were unvaccinated.

Half of six patients treated in the Royal Adelaide Hospital fought for their lives in ­intensive care.

A cleaner attending to the deep clean of the Greek on Halifax Street. Picture: Emma Brasier

Entrance to the closed Tenafeate Creek Wines cellar door and vineyard at Yattalunga near Gawler that has a lot of new COVID cases. Picture Mark Brake

The average Delta strain infection time was a “rapid” three-day incubation, compared with four or five days with other variants. One patient fell ill after a fortnight.

Chief public health officer Professor Nicola Spurrier said the review would improve strategies to protect South Australians.

“The threat of Delta to our state is real and those who aren’t vaccinated face a significantly increased risk,” Professor Spurrier said.

“This outbreak highlighted just how sneaky the Delta (strain) … is and how many challenges this variant poses when community infection arises,” she said.

Contact tracers recreated gatherings at the Tenafeate Creek Winery, Yattalunga, on Sunday, July 18, and the Greek on Halifax restaurant the night before.

Restaurant customers and staff easily caught the virus amid an “attack rate” of 22 per cent in a private dining room.

A guest among a party of 11 was “visibly symptomatic and coughing” in the confined room, the review found.

Almost three-quarters of 131 restaurant guests had not received a jab.

A similar proportion of the 82 people who visited the winery’s Barrel Room between 2pm and 4.10pm were unvaccinated. Dozens failed to check in at both spots.

The cluster, which plunged SA into a seven-day statewide lockdown on July 20, forced almost 6000 people into 14 days’ quarantine after visiting 76 exposure sites.

The layout of the Tenafeate Creek winery, showing where infected people sat.

The layout of the Greek on Halifax, showing how Covid spread through the restaurant.

After interviewing patients, authorities reviewed QR code data, phone geolocation records, financial transaction details, staff ­rosters and CCTV footage to track contacts.

Nearly 26,000 people were linked through shops, schools and TAFE campuses.

The report said the cluster’s index case was a grandfather, 81, who travelled from Argentina to Sydney on June 23. The source of his infection was unclear, but “likely” emerged in NSW.

Possible exposure points were his Sydney medi-hotel, a Sydney hospital or in transit to Adelaide.

No breaches were identified and the pensioner, from Buenos Aires, had many negative tests before travelling to SA in late June.

He was rushed by ambulance to Modbury Hospital late on Sunday, July 18, before a positive result the next day.

His family have declined to comment.

Professor Spurrier declared the outbreak over on August 30.

Hospital staff watch Premier Steven Marshall along with SA Health Minister Stephen Wade, Professor Nicola Spurrier during the Covid update press conference at the Modbury Hospital. Picture: NCA Newswire/ Kelly Barnes

MODBURY CLUSTER BY NUMBERS:

• 22 infectious patients.
• 13 men and nine women aged between two and 87. The cluster’s index case, a grandfather man, 81, who flew from buenos airesto Sydney on June 23, before presenting at Modbury Hospital with his daughter, aged in her 50s, on July 19.
• Seven cases were partially vaccinated, 14 unvaccinated and one unknown.
• Six patients treated in Royal Adelaide Hospital including three in its intensive care unit.
• 76 public exposure sites.
• 127 contacts from family and other social interaction.
• 215 contacts linked to The Greek on Halifax restaurant on July 17 – 128 attended location.
• 189 contacts linked to the Tenafeate Creek Winery, Yattalunga, on Sunday, July 18 including 82 in Barell room.
• 25,847 contacts identified from QR check-in data linked to all exposure sites.

Source: SA Health