The Holiday Inn quarantine hotel outbreak has grown to 13 – with two more people testing positive late on Thursday – as authorities worked into the wee hours to identify more exposure sites.

The fresh infections linked to the Melbourne Airport hotel cluster were announced overnight and are both household primary close contacts of previously confirmed cases.

Another location at the airport has been added as an exposure site. Anyone who was at Brunetti cafe in terminal four between 4.45am-1.15pm on Tuesday, February 9, has been told to get tested and isolate for 14 days.

The latest cases came after three people were added to the outbreak earlier on Thursday – two male spouses of Holiday Inn workers and a female assistant manager at the hotel.

Anyone who visited this location must isolate, test and remain isolated for 14 days.
For a full list of exposure sites and locations where you can get a #COVID19 test, visit: https://t.co/ogHDjdmEZd#EveryTestHelps

— Victorian Department of Health (@VicGovDH) February 11, 2021

Health officials believe the outbreak started via mist from an undeclared nebuliser used inside the room of an infected family of three.

The first six cases have all been confirmed as the same British virus strain. Authorities are working on the presumption that the outbreak’s 11 earliest cases are the same variant.

But as experts explore the theory of airborne transmission in quarantine hotels, a top infectious diseases expert has come under fire for suggesting aerosol transmission of the coronavirus is still up for debate.

On the ABC’s Q+A on Thursday, former deputy chief medical officer Dr Nick Coatsworth said there was “a live debate about the extent to which COVID-19 is transmitted via the aerosol route, via aerosols of COVID-19 that are inhaled”.

His comments were in response to epidemiologist Tony Blakely calling for “federal guidance around aerosol and its impact in [hotel] quarantine”.

Dr Coatsworth’s suggestion drew criticism from fellow Q+A panellist Dr Michelle Ananda-Rajah, who is associate director at the Monash Institute of Medical Engineering. She said he was “wrong”.

“I’m taking issue on it that it’s a debate,” Dr Ananda-Rajah said.

“We’re 14 months into this and we’ve had real lack of movement on acknowledging the fundamentals of disease transmission.

“If you don’t acknowledge that this is spread through the air, through a mixture of droplets as well as aerosols, you can’t really slice where a droplet, what a droplet is and what an aerosol is.

“If you can’t acknowledge it, you can’t prevent it.”

Dr Coatsworth, who was one of the early faces of the federal pandemic response, then said he agreed there was an “element of airborne transmission”.

Clock running down to contain outbreak

An epidemiology expert said it was good news that the Holiday Inn infections so far were linked but the outbreak would require an urgent response.

“This will be a real test of the contact tracing network that the Victorian government has set up,” said Dr Alex Polyakov, a senior lecturer in obstetrics and gynaecology at the University of Melbourne who holds a masters in epidemiology and biostatistics.

On Thursday afternoon, three more people who tested positive to the virus were already in isolation when their positive test came back.

“That’s the way to do it, because they have isolated all the close contacts of those people so hopefully even if there are further infections they will already be in isolation,” Dr Polyakov said.

But the British B117 strain was certainly a concern, he said.

“Not a lot of information is known about [the new strain], but it appears to be more infectious so it would have a higher risk of transmission,” Dr Polyakov said.

“I think it’s probably very fortuitous that we haven’t seen a much larger outbreak as yet. But there’s still a chance there are people in the community who haven’t been tested, but who are positive and may be spreading the virus further.”

Health authorities are working through exposure sites for the most recent infections, and have boosted testing across Melbourne.

• The full list of current Victorian exposure sites is here

“I encourage people to keep coming forward. We are still at an early stage of this Holiday Inn outbreak,” Victorian testing commander Jeroen Weimar said on Thursday.

“We are still trying to get a sense of how far transmission has already occurred and we need to be sure we keep running faster than the virus to ensure we run it to ground.”

It will take two weeks from the initial diagnosis to find out just how far the virus has spread, Dr Polyakov said.

The Holiday Inn outbreak began with one infected family, and has spread to workers and former guests. Photo: Getty

“If there are no community cases, that means this outbreak has been contained,” he said.

“If there are community cases, then the tracing needs to work really well to make sure there is some sort of ring of steel around those people who are infected so it doesn’t get out of hand.”