The daily coronavirus stats in Wales are not very useful for providing an accurate picture of what is actually going on.

Let me explain/bore you to death:

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From the very start of the pandemic, the main place people would go to see how the virus was progressing in Wales was the daily updates from Public Health Wales.

Throughout the crisis this has been the go to place for information.

The latest figures paint quite a concerning picture of Covid in Wales. Despite a fall in cases over the Christmas period, they now seem to be rising again.

You can see how the data has changed here:

So what is going on?

There is a lot going on behind this graph that we need to take into account and explains why the Welsh Government are totally unclear on whether schools reopening on January 18 is remotely feasible.

The first thing we need to look at is testing.

Take a look at this graph that looks at the number of tests and the number of cases done in Wales in December:

As you can see, Wales was averaging about 13,000 tests a day through out the first three weeks in December.

However over Christmas this plunged to just 4,000.

The dip is to be expected, who'd want a test on Xmas day? But it does account for why there was a fall in the number of cases and why it has gone up since Xmas.

We also saw a surge in tests just before Xmas (presumably as people wanted to get checked before seeing family).

There is more to this than just the amount of testing.

The confusion over what impact different restrictions have made in Wales is even harder because of how the restrictions have been introduced.

If you cast your mind back to the first wave there was a crucial difference in how we went into the lockdown.

On March 23 the UK as a whole went from no real restrictions (some things had already started to close but much was just advice), to a full on total lockdown.

The same was true for leaving lockdown where Wales in particular had a very slow, methodical, three week cycle to lifting restrictions - meaning it was far easier to see cause and effect. It was the same with the fire-break.

This time around it is different.

Since the start of December all these events could have had a meaningful impact on case numbers:

Dec 4 - Hospitality close from 6pm & booze ban
Dec 11 - All secondary schools closed in Wales
Dec 20 - Level 4 lockdown introduced (except retail)
Dec 24 - Non essential retail shut

As we have seen with the firebreak it can take over 10 days for the effect of any changes to been seen in the figures.

This means that all of these different factors could only now be impacting on the current data (or having no impact at all).

Plus we need to add to this the mass mixing over Christmas and possibly New Years Eve which will be exerting upward pressure on the figures.

And then we have the new strain which the Welsh Government believe is driving the rises in the north of Wales.

So when will we know what is happening?

That is a very good question. With school not reopening until January 18 at the earliest there is not really any further to go in terms of new measures. This means we should start to see a trend developing soon.

ATM testing positivity is key (AKA the % of tests that are positive).

This is a good indicator of the amount of the virus circulating in the community.

Back in July this was regularly well below 1%.

Now it has been over 15% since the start of December.

This figure did not fall over Christmas as you can see from this graph:

If positivity remains high it suggests the fall in cases we have seen may not be the cause for optimism we hoped.

The upshot of this uncertainty is that the WG aren't 100% clear on what the current picture is in Wales making it hard to work out the impact of particular measures.

What we can say with some certainty is that Wales is no longer the worst hit part of the UK.

If you got this far down the thread I would be amazed.

You can see the full details here with interactive graphs: https://www.walesonline.co.uk/news/politics/stats-data-coronavirus-covid-cases-19571252