One of the difficulties in determining how to respond to the Coronavirus epidemic is a lack of evidence with which to base decisions. But since some countries – most notably China, South Korea and Italy – are ahead of the UK’s trajectory, there are lessons emerging which could inform decision-makers.

For example: what is the effect of placing areas in a lockdown?

It’s an imperfect analysis, but the following graph shows the trajectory of the total number of cases in two provinces of Lombardia.

The regions are broadly similar geographically and demographically, so it’s not totally unreasonable to consider them as equivalent when making comparisons. However, Lodi started with more cases and was placed in a  state of lockdown as of 23 February. Bergamo was also placed in lockdown, but considerably later, on 8 March.

Looking at the figure, though the number of cases has grown in both cases, in Lodi the growth is more or less linear, with signs of levelling off. In Bergamo, the growth appears to have started at an exponential rate, with a change to linear growth soon after the lockdown there, but with a steeper rate than that of Lodi. If it’s fair to make a direct comparison between these two provinces, there’s strong evidence that locking down early has a considerable impact on an epidemic’s growth.

Of course, there are a number of other factors to take account of, some of which may favour Bergamo over Lodi. People’s freedom of movement has been maintained for a longer period in Bergamo, and the effect on the economy is likely to be slighter – at least in the period shown in the graph. And we don’t know what will happen in the future – maybe when things are eventually relaxed the number of cases will grow faster in Lodi than in Bergamo.

Nonetheless, by the strict measure of short-term growth of epidemic, the evidence here is that an early and comprehensive lockdown is an effective strategy in containing numbers of new cases.

As I’m writing this I’ve just heard Boris Johnson announce a nationwide voluntary restriction on social contact in the UK. Time will tell whether this is stringent enough to get the same braking effect on the epidemic growth as was achieved in Lodi or if – as in Italy nationally from last week – a legally enforceable version of a lockdown will prove necessary.

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