This chart shows how the Covid-19 outbreak
has spread through England and Wales since early March.
Horizontally, on the x-axis, we see the number
of new cases per day, per 100,000 people,
in every area, every local authority in England and Wales.
Vertically, we're showing that as a rate
of change, a rate of increase.
So the higher up a point is, the more quickly its new infections
were increasing.
The lower down, the slower the rate of increase, or perhaps
cases were actually declining.
In early March the coronavirus was spreading through England
and Wales at a rapid rate.
Numbers of cases that have been picked up were relatively low,
but the rate of increase was extremely high.
Nationally, new cases were increasing
week-on-week at a rate of seven or eight times.
Moving later into March that rate of increase
began to taper off slightly.
But as the increase fell the numbers of cases grew.
And soon we had many communities in England and Wales
with more than 10 new cases per day, per 100,000 people.
Moving into April, that rate of acceleration
continued to diminish slightly, but we are now
moving towards the peak of confirmed cases
in the community, with several areas now seeing
more than 15 new cases per day per 100,000 people - incredibly
widespread infections.
Moving from late April into May, both of those numbers
started to go down as we moved past the peak.
Numbers of new infections were decreasing,
and therefore, that rate of change
was actually moving slightly negative.
But you can see that we still had some communities, hovering
around on the right-hand side there,
with elevated rates of infections per day.
Among those was Leicester, which became
famous for its second lockdown in June.
You can see here how Leicester's rate of infections
was never especially low.
It maintained that background level
of infection, which then increased through
into early and mid-June.
It's been joined then by more places that
had very different outbreaks.
We see the meat processing factory outbreaks
of the likes of Wrexham, Anglesey, and Merthyr
Tydfil in Wales.
But all of those were very short-lived.
Note how the points jump out there to the upper right
but then quickly fly down into the lower left.
Here we are now in July.
You can see that we now have that community spread going
on in places, still like Leicester, although it's down
from its peak, and also places like Blackburn, Rochdale,
and Bradford.
The question now is whether cases
will continue to fall in those areas
or whether that community spread might expand further.
One of the things we've seen here
is how different places have very different types
of outbreaks, different shapes of outbreak we might say.
You've seen the dots for places like Herefordshire, Anglesey,
Merthyr Tydfil, and Wrexham, which shot into the upper right
and then quickly back down into the bottom left.
This is what it looks like when you have an isolated
cluster, something like an outbreak at a farm
or a meat processing factory.
Cases suddenly shoot up when a large number of people
are suddenly detected in one fell swoop.
And then as long as the outbreak hasn't
spread into the community, cases fall very quickly as well.
These are better outbreaks to deal with,
in the sense that they're small, they're isolated, there's only,
generally, one place that has to be tested.
If those outbreaks are contained they come straight back down.
That's in contrast to outbreaks like the one we
saw in Leicester and also the higher rates of infections
we've been seeing in places like Blackburn.
What's going on there is you have
what we call community spread.
There's a slower increase, a more gentle slope upwards,
as it were, a longer period with high infections, and then
a slower decrease.
This is because the virus is spreading from person to person
more widely in the community.
There's no single, large outbreak.
These outbreaks can be harder to track and trace,
meaning that they're more dangerous to the wider society,
and there's a risk, if community spread is not
controlled, that they can spread further and turn into regional
or even national outbreaks, just like the one we
saw across the whole of the UK back in March and April.
The data used in this chart comes
from Public Health England and Public Health Wales.
The key thing to note here is that that data
uses specimen date when we talk about timings.
So that's the time, the day, when the swab was actually
taken from someone.
It's as close to real-time information
as we get on when new cases are being confirmed.
All of the FT's coverage on coronavirus,
whether it's data-driven pieces like this or more deeply
reporting stories, is free to read on ft.com.