A mathematical modeling study evaluating border controls for COVID-19 reincursion risk found that a period of $$ 14 $$ days of managed isolation or quarantine (MIQ) reduces the risk of releasing an infectious case into the community to a very low level. Combined with testing on day $$ 3 $$ and day $$ 12 $$, daily symptom checks, and complete isolation of confirmed cases, the risk is approximately $$ 0.1 \% $$ per arriving case. The greatest reduction to risk involves minimizing interaction among arrivals.

Northwestern University

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This study investigates the effectiveness of New Zealand's travel restrictions- specifically the closing of the border to everyone except citizens and residents. It then analyzes 7 different extremes in terms of travel restrictions and models what their effects would be on the amount of re-incursion from international arrivals. 
- Background information
- Results from Observed Data
- Future: 7 scenarios
- Discussion

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

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

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

From 9th June 2020, arrivals in New Zealand MIQ facilities have been tested twice, once around day 3 and once around day 12 (Ministry of Health, 2020). We consider the two-week period between 23rd June and 6th July, during which all individuals have been subject to these requirements for their entire stay. 

Results from Observed Data

Impact of Managed Isolation and Quarantine on COVID-19 Reincursion Risk

New Zealand imposed strong border restrictions, forbidding all non-residents since March $$ 20 $$. All arrivals have a $$ 14 $$-day imposed quarantine in government facilities where they are monitored and tested for COVID-19 on days $$ 3 $$ and $$ 12 $$. Now that restrictions have been lifted, it is critical to consider the impact that overseas cases may have, as a rapid outbreak may occur. This study utilized mathematical models to predict several outcomes.

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