This morning, the Taoiseach and his Government announced a national shutdown of Schools and other public places for an initial period of two weeks, along with a nationwide programme of social distancing. It was the right call.

But it’s worth asking: How long could this shutdown actually last? Does the Government have some benchmarks for new cases of COVID-19 that it wants to see before it re-opens schools? Is this a one-shot plan that it hopes will work, or is there potential for it to be extended?

We don’t know those answers right now, but we do have some clues.

First, it’s very clear that later this evening the Department of Health will release new figures for infections, and that those numbers will show some kind of significant increase on yesterday’s. Last night, we had nine new cases, bringing us up to over 50 in total in the Republic. What will tonight’s show?

Here’s the graph of cases to date, courtesy of Wikipedia:

And here’s the same graph for Italy:

If the virus is on the loose in the population, we should expect to start seeing a sharp rise in Irish cases, but it won’t be linear. The general rule thus far, without strong containment measures, has been that it would double every six days. So if that rule holds, Ireland should be at 100 or more confirmed cases by next Monday. It would be 200 by the following weekend, and then it should double again six days after that.

So, without the containment measures, you’d expect Ireland to have 400 confirmed cases by March 29th. So that’s a reasonable benchmark for us amateurs to follow along with. It’s not anywhere close to perfect, but it’s about the best we have.

Of course, the impact of the measures may not be felt for some time. Remember: It’s a certainty that there are many people out there who have the virus but who do not know it yet. You also will have the continued impact of people coming home from places like Cheltenham, etc, or stragglers coming back from overseas and carrying it with them. Those people are likely to infect, at minimum, the people they live with.

So 400 by March 29th still seems like a reasonable projection, even with the containment measures.

In fact, it’s very possible that it will be hard to tell, at all, whether the measures are working within two weeks.

One Italian town that introduced containment two weeks ago reported no new cases for the first time yesterday. Two weeks is about the minimum amount of time it takes to slow the spread. But because there are still sick people, they’re not lifting the measures.

So what will the Government do on March 29th? It’s impossible to say. But it’s a reasonable bet that the schools will be closed for a bit longer than two weeks.