Urban economists like to brag about how cities are more productive than other areas because of `economies of agglomeration’ which reduce the cost of physical contact, as people are closer together. The cost of that closeness is increased sharing of the air between people, and the airborne viruses that reside in it. Viruses physically move from one person to another. Just as the likelihood of interaction between two people is inversely proportional to the distance between them, the likelihood that viruses are transmitted between two people is inversely proportional to the distance between them, as the longer the virus is exposed to colder out-of-body temperatures and sunlight, the less likely it survives AND the nearer two people are, the sooner a virus can go from one person to another. This is just accessibility.
So, putting people close together in hotels to quarantine them, assuming some have the virus, is obviously going to increase the likelihood of transmission between hotel residents compared with putting them farther apart in camps.
And putting these hotels in cities is obviously going to increase the likelihood that a virus from the hotel interacts with the city around it.
So if the intent is public health, quarantined people should be kept far from each other and from non-quarantined people.
Fortunately Australia is a big country. There are many opportunities to quarantine people away from each other and away from others. Unfortunately, people are being quarantined in the middle of cities inside of hotels.
The latest outbreaks in Sydney and Perth should not be surprising. That this was the policy in April of 2020, when everything was new would be understandable. That this remains policy in April of 2021 when it is not is puzzling.
If quarantine sites were remote, and the likelihood of transmission reduced further, perhaps Australia could increase its intake of stranded citizens, international immigrants, and students.