When and how to end the lockdown?
THREAD on likely scenarios.

As many countries start seeing a levelling or decrease of new cases, the possibility of ending lockdowns start being discussed.

First observation: the road to eliminating the epidemic may be long. See S. Korea

For a country like Australia, which has been very successful at controlling the epidemic, it is not clear whether numbers can fall down to zero quickly or remain positive for weeks like in S. Korea.

source: https://www.worldometers.info/coronavirus/country/australia/

Nonetheless, as numbers go down further, what are the options ahead?

By increasing testing, isolation of new cases and and tracing of their contacts, it may be possible to keep the reproduction number R<1 with social distancing measure not as harsh as a full lockdown.

The trade-off : Economic benefits/cost vs risks of a second wave.
See how Singapore seemed to have the infection numbers seemed to go down end of March, and then they went up strongly (no lockdown).

Activities requiring large gatherings are the most risky. They can spread infections. And if a new case is acquired in a large crowd, it cannot be traced back to its source.
Sporting competitions, cinemas, concerts, bars, conferences should not be considered for some time.

Only exception are schools. The closure of schools immobilises many parents at home, it has a much larger economic costs than other closures (e.g. stadiums, cinemas).
As cases drop, schools are likely the first place of gathering to re-open.

Sensible scenario: as cases trickle down, case-free areas would see restrictions lifted first.

It would involve keeping national borders closed, minimising travel across regions/states within the country.

New infections could be isolated locally, with new restrictions.

A big challenge is that many cases are asymptomatic, so even if an area does not have new cases for a few days, asymptomatic cases may remain in the community for some time.
For that reason, the lifting of restrictions should be slow to prevent a new wave.

In any case, there should not be a full end of the lockdown in the short term. And the public should be wary of calls for mass gathering activities (e.g. sports, bars) to restart soon.

Social distancing, social protection (hand washing, masks), should stay, possibly for months.

End game?
Herd immunity is not a clear option as several people have been re-infected in S. Korea and numbers suggest only a small proportion of the population may have been infected in most countries.

Fully eliminating the epidemic is also hard. Even a country ending local cases will face risks from cases coming from abroad. So restrictions of some kind, in particular on international and regional travels will likely be maintained.

If so, the true end game will be finding anti-viral medicine or a vaccine.
Vaccine has to take several months: you can’t inject a vaccine in millions of people without having carefully tested its effects first.
But the global research effort is impressive:

Carefully optimistic view: an anti-viral medicine (only used with patients) may help before a vaccine. Given the massive research efforts, some treatments could be found sooner rather than later. They could reduce deaths and hospitalisations and facilitate return to normal life.

So, things are looking better in many countries. But we should be wary of calls for a quick removal of the lockdowns. The cost of easing restrictions too early is likely greater than the cost of easing them later than necessary.

END