The airport's managing director, Stephen Byron, said the ACT government's approach to border restrictions was the "gold standard" which had helped restore confidence in interstate travel. Other premiers, Mr Byron said, "could do well" to follow the ACT's lead and impose restrictions for only as long as they were necessary.

His implicit criticism of other states was echoed by Qantas chief executive Alan Joyce who is baffled by how Victoria can let in a thousand people for the Australian Open tennis tournament while keeping its border closed to visitors from NSW.

It was "out of proportion with the actual risk" from NSW, he alleged.

The word "proportion" is important. Nobody argues that borders shouldn't be closed or only closed as a very last resort. Rather, there should be a finely-tuned approach, proportional to risk.

In the ACT, the result of a more calibrated response to external risk has been a surge in passenger numbers at Canberra Airport. The economy has not been slammed shut to rule out all risk.

Elsewhere, borders have been closed with what seems like too much alacrity. State leaders seem to have erred on the side of political caution in closing off travel, and travel is, after all, a generator of economic activity.

Last year, it was notable that some of the toughest border controls were imposed by the Northern Territory and by Queensland, both of which had elections. A sceptic might wonder if the political desire to appear tough in voters' minds determined how the border closures operated.

To their credit, the leaders of the ACT government (and the opposition candidates to replace them) also had an election but didn't resort to competing assertions of toughness involving border closures.

Of course, the ACT is a small island which needs the surrounding economy and its dollars more than the big states need the economic activity from their neighbours.

But the ACT policy has been measured. In effect, it shut its borders to Sydney on January 2 with the outbreak there, but it didn't seek a wider shutdown of traffic from non-affected areas. This week's lifting of restrictions on the Central Coast and Wollongong was similarly reasonable.

Contrast that proportionate policy with Victoria's decision to ban virtually all travel from NSW as the Sydney outbreak raged. It meant that people from Queanbeyan couldn't enter Victoria even though the NSW town is virtually a suburb of the ACT from which travel was acceptable.

We are learning how to deal with outbreaks. Instead of the cudgel, the scalpel is better. Address hot-spots and not whole regions is a better way to minimise economic damage while containing an outbreak of infections.

The key is to be able to act quickly and with focus. Borders need to be blocked quickly - and unblocked quickly. This creates difficulties for travellers who want to plan their movements but we are learning to live with that. Plans are conditional.

The longer this epidemic goes on, the more it becomes clear that even a vaccine won't bring a return to what we once thought of as normality. Experts talk of containing the epidemic and not of eliminating it.

Common sense and a proportionate response are the keys.