Coronavirus Scotland: Five graphs which explain the key Covid-19 statistics in Scotland right now

The number of people in hospital with Covid and the number of new daily admissions is one of the clearest signals of what is happening in the pandemic.

It cuts through 'false positives' known to occur in the PCR test (because only people who are genuinely infected are going to become sick enough to end up in hospital), and a significant rise in admissions alerts us that the virus is spreading among more vulnerable groups. 

Today, the Nicola Sturgeon noted that we "are not yet seeing an increase in hospital admissions on anything like the same scale that we saw back in the spring".

READ MORE: Meet the student blogger behind Scotland's most popular Covid tracker site 

This is partly because the highest proportion of new cases in recent weeks has been in people under the age of 40, said the First Minister - though this is changing.

"We know that transmission in the community cannot rise indefinitely, without it starting to increasingly affect older people too," she said. 

"And we are now  an increase in the number of people admitted to hospital and in intensive care – albeit from a fairly low level." 

The above graph shows that the number of people in hospital with Covid-19 has increased from 45 on September (including six patients in intensive care) to 63 (with nine patients in ICU as of yesterday).

As of today, that number has risen to 73 - with eight patients in ICU. 

The 'Patients in Hospital' figure was recently revised to include only patients who have tested positive for Covid within the past 28 days.

Previously patients who had tested positive at any time had been included, meaning people could have tested positive months ago, recovered, and been re-admitted to hospital for an unrelated condition.

However, the revisions also meant that patients who take a long time to recover and are still in hospital more than a month after falling ill with Covid will be missing from the daily figures. 

The 'patients' in hospital' data will fluctuate day to day, influenced both by new admissions and recovered Covit patients being discharged from hospital.

Another important way of looking at the data is on the basis of daily admissions. 

The above data, from Public Health Scotland, illustrates that despite recent increases, the picture in Scotland remains very far from the peak in early April.

Looking at the seven-day averages for daily admissions, it is possible to chart how admissions have changed week to week through the pandemic. 

In the week to April 6, there had been an average of 184.3 people newly admittd to hospital with Covid each day. 

By July, fewer than one patient a day was being admitted on average.

And despite the recent increases, in the week ending September 7 - the most recent period for which data is available - Scotland has been averaging just three admissions for Covid per day. 

These are patients who test positive for Covid on admission, or in the 14 days prior to hospital admission.  

POSITIVE CASES AND POSITIVITY RATE 

The number of new positive cases is the headline figure each day. 

This has increased as testing has expanded, so the volume of infections being detected now is not directly comparable to the peak of the pandemic, when testing was concentrated in the hospital setting. 

However, charting the data from the beginning of August allows us to see how the picture has changed during a period when testing has been open to anyone in the community with possible Covid symptoms. 

In the week ending August 2, just over 22,000 people who had been newly tested for the virus received their results, and just 125 people were found to have Covid.

In the week ending September 6, the number of individuals receiving test results peaked at more than 83,000 - with 1,079 positive cases detected.

More recently, backlogs at the Lighthouse laboratories have slowed turnaround times and in the week to September 20, the number of people receiving test results had fallen to 40,452.

However, even in that smaller sample size there was evidence that the prevalence of the virus was climbing, with 1,692 positive cases identified. 

One of the clearest ways to track the prevalence of the virus in the community is the percentage positivity. 

This tells you how many cases are detected for every 100 people tested. 

If the proportion consistently exceeds 5% over two weeks, the World Health Organisation considers this a warning that the amount of virus spreading in a population is beginning to outstrip the ability of a country's testing resources to contain it.

The most recent percentage positivity for Scotland - based on the 255 new cases announced today - is 6.3% - and, according to the First Minister, higher still in some health board areas. 

READ MORE: Younger Scots make up fifth of hospital admissions for Covid since early August 

However, Ms Sturgeon cautioned that this should also be understood in the longer context of the pandemic. 

"The number of cases is not rising as quickly as it was in the spring, and the percentage of positive tests, while rising, is nowhere near as high as it was back then," said the First Minister.

"Back in those days it was 20% or thereabouts."

On a week-to-week basis, as the graph above shows, percentage positivity climbed slowly from 0.6% for the week ending August 2 to 1.3% for the week ending September 6, before accelerating more recently - to 2.5% in the week ending September 13 and reaching a new high of 4.2% last week. 

EXCESS DEATHS

Research for the Office for National Statistics revealed that Scotland had recorded the third highest excess death rate in Europe - after England and Spain - during the first half of 2020. 

This is considered to be one of the most important statistics for evaluating how well a country has coped with a pandemic. 

Under this measure all deaths, from any cause - including, but not limited to, Covid - can be counted and compared against the five-year average for the same period. 

This gets around the problem of whether or not individuals were tested for the virus, and means that collateral damage - such as people dying from heart attacks because they avoided going to A&E during the crisis - will be reflected. 

For most of July, the number of people dying in Scotland tended to be below average: between June 22 and and July 26, there were 81 fewer deaths than normal. 

During that same period, however, there were 50 deaths from Covid - according to death certificate figures collated by National Records of Scotland.

In recent weeks, that picture has shifted again. 

In the period from August 17 to September 13, a total of 203 more deaths than average have been recorded in Scotland - yet just 11 of these were Covid deaths. 

It is unclear exactly what has driven this upsurge: deaths from cancer, respiratory illnesses and dementia, are all down for example. 

Only 'circulatory deaths' - typically hearts attacks and strokes - and, in particular, deaths from miscellaneous 'other' causes have gone up. 

This may point to a continuation of patterns already noted by Public Health Scotland when it analysed the excess death data up to June 15 and found evidence of a "striking" increase in deaths from causes including violence, road accidents, drugs, alcohol and suicide.

PHS stated: "The measures taken to control the spread of Covid-19 may also have had negative economic and social consequences in the wider population, with implications for mental health and coping strategies that may be reflected in excess external and ill-defined causes of death (e.g., drug-related deaths, alcohol-related deaths, and suicides).

"The reduced traffic volumes and the closure of establishments serving alcohol for consumption on the premises during the period might have been expected to lead to a decrease in deaths from traffic accidents and violence, which makes the increase in deaths from external and ill-defined causes even more striking."

It remains to be seen what lies behind the increase seen in recent weeks.