Melbourne’s hotel quarantine cluster has grown to 13, with two more Covid-19 cases reported late on Thursday.
The latest cases were people living with someone who had previously tested positive and were already isolating.
However, a Melbourne airport cafe has been added to the list of exposure sites connected to the Holiday Inn outbreak.
Earlier on Thursday, a female assistant manager at the hotel and two men, both partners of female food and beverage attendants, tested positive in the first cases of secondary transmission in the community linked to the outbreak.
The cluster is now made up of three staff, two former guests, four close contacts and a family of three who were the original index cases and likely acquired the disease overseas.
The outbreak had forced the closure of the Holiday Inn, while plans to increase the state’s weekly cap on international arrivals from 1,120 to 1,310 from next week were put on hold.
Victoria’s chief health officer, Brett Sutton, said authorities suspected the cases were linked to the use of a nebuliser, a device that vaporises medication or liquid into a fine mist.
“If that’s breathed in and someone is infectious or later tests positive, then that picks up the virus and then that mist can be suspended in the air with very fine aerosolised particles,” he told reporters on Wednesday.
The nebuliser was used by one of the family members, who has an underlying health condition and was taken to intensive care on Tuesday.
Sutton said it was possible everyone on that floor of the hotel had been exposed to the virus.
The Covid-19 Quarantine Victoria commissioner, Emma Cassar, said the guest had not reported the nebuliser when arriving at the hotel, and would have been taken to a medi-hotel if they had.
The premier, Daniel Andrews, said: “I’m sure they didn’t believe they were doing the wrong thing, but we are taking extra steps to make sure those machines are not in the hotel.”
The Australian Medical Association national president, Omar Khorshid, said the UK variant had “blown open cracks” in hotel quarantine infection controls, exposing the need for urgent action.
“We are incredibly lucky to have not yet seen a mass outbreak,” he said.
More than 950 hotel quarantine staff across the state were isolating.
Just after midnight on Thursday morning, South Australia chose to lock out travellers from greater Melbourne. Returning SA residents, people relocating and other exempt travellers would still be allowed in but would need to quarantine for 14 days.
SA’s chief health officer, Nicola Spurrier, said she was “very concerned” by the Victorian outbreak, comparing it to the Parafield cluster in South Australia, which prompted a snap lockdown.
The Western Australian premier, Mark McGowan, said his state would keep its border shut to Victoria for another seven days due to the Melbourne outbreak.
Queensland has not shut the border but people coming from Victoria would need to fill out a border declaration form. Most states and territories had listed the Holiday Inn hotel as a hotspot.
Queensland’s acting chief health officer, Dr Sonya Bennett, said anyone who had been in one of the greater Melbourne exposure sites should get tested and quarantine for 14 days.
Those who had been in the city on or after 5 February but had not been to those exposure sites should still get a test and isolate until receiving a negative result.