Establishment of biosecurity zones could allow different regions of Ireland to safely emerge from lockdown at different speeds

The Northern Ireland Executive announced their roadmap to relaxing coronavirus restrictions today, following similar publications for England and the Republic of Ireland. Unlike the Irish government’s plan, no dates were released with the plan, although there is an aspiration to progress through the plan’s five stages by the end of 2020.

Progress on lifting restrictions depends on the all-important R0 figure, the number of people with Covid-19 who subsequently infect others. However, calculating R0 is difficult and necessarily imprecise. An alternative way of measuring the spread of the virus is the doubling time, the number of days taken for the number of cases to double.

The maps above show the number of reported Covid-19 cases per 100,000 people for counties in the Republic of Ireland and council areas in Northern Ireland. Across all of Northern Ireland, the case doubling rate is 69 days, whilst in the Republic the rate is 80 days, indicating that growth is slower in the Republic. For comparison, countries that have been comparatively successful such as South Korea and Germany have case of doubling rates of 299 and 134 respectively. The rate across the UK as a whole is 33.6, indicating that growth of cases in England is substantially higher than both Northern Ireland and the south.

The table below summarises the data from the charts; I wasn’t able to work out the case doubling rate for County Limerick as the case count data had been revised.

Differences in the amount of tests carried out on both sides of the border means that caution is needed when comparing data between the two jurisdictions. However, there is enough data to suggest that the Republic have had more cases per capita than Northern Ireland since the start of the outbreak, but that cases are now growing at a slower rate.

However, the westernmost council areas of Northern Ireland (Derry City and Strabane, and Fermanagh and Omagh) have both had low case numbers overall and are now showing signs of having significantly slowed the growth of new cases.

For the seven days to the 12th of May, both of these council areas have only had five new cases each; there have been 302 cases in the rest of Northern Ireland over the same period. If such low case growth is sustained, then it should be possible to implement the “test, trace, isolate” phase in these areas and partially release the lockdown even if case growth in other areas remains too high to consider easing restrictions.

If a “biosecurity zone” was created, encompassing the two westernmost council areas, with a mandatory 14 day quarantine required for anyone other than essential workers entering the zone, then it may allow restrictions to be eased more quickly in this area whilst mitigating against the risk of a second wave of infections. Similar quarantine restrictions for anyone entering other areas of Northern Ireland from the Republic of Ireland, Great Britain or elsewhere could be implemented at the same time.

The next stage of the battle against the coronavirus will require proper implementation of the “test, trace, isolate” plan, effective use of contact tracing apps, and may require uncomfortable restrictions on freedom of movement.

The wasted opportunity at the start of March whilst the British government pursued its now-discredited “herd immunity” strategy will be forever lost, but for one reason or another Northern Ireland seems to have had fewer cases per population than other places in these islands over this initial phase of the pandemic. As the lockdown is gradually eased, consideration should be given to adopting a localised approach and moving at different speeds.

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