Testing only upon arrival only detects 53% of arriving infected cases. 

Northwestern University

7 scenarios were mathematically modeled in order to predict what the pandemic will look like New Zealand once border reopen.
- Scenario 1: Test on Arrival Only
- Scenario 2: Test on Arrival and Departure
- Scenario 3: Five Day Quarantine 
- Scenario 4: 10 Day Quarantine 
- Scenario 5: 14 Day Quarantine (Currently being employed)
- Scenario 6: Exemptions Allowed
- Scenario 7: Late Exemptions Allowed

7 Scenarios

Steyn N., Binny R., et al. The effect of border controls on the risk of COVID-19 reincursion from international arrivals. 22 July 2020. BioRxiv. https://doi.org/10.1101/2020.07.15.20154955

The effect of border controls on the risk of COVID-19 reincursion from international arrivals

Extending the quarantine to 10 days is equivalent to 1 highly infectious case being released into the community every 100 days on average.

Scenario 4 Model

A 5-day quarantine period detects as many cases as the full 14-day period but is not as effective in preventing highly infectious cases reaching the community. A 5-day quarantine leads to 6.8% of arrivals who are highly contagious being inappropriately released. This is equivalent to 1 case reaching the community every 9 days. 

Scenario 3 Model

Testing only upon arrival and departure detects 64% of arriving infected cases.

Scenario 2 Model

Scenario 1 Model

Extending the quarantine to 14 days (which is the current policy) equated to 1 highly infectious COVID-19 case being released into the community every 600 days. If interpersonal contact is allowed within the quarantining facilities, this risk can rise to 1 every 27 days, which is why separating people during quarantine is essential.

Scenario 5 Model

Exemptions do pose a small risk, especially early exemptions lowing for early exemptions which may release highly contagious cases into the community. Therefore reducing interpersonal contact within the government quarantine facility is essential.

Scenario 6 Model

Late exemptions (in the second week only) pose less of a risk since the individual has been quarantined for a significant amount of days already. 

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