What do the statistics really tell us about UK coronavirus deaths?

The UK has recorded more than 1,200 coronavirus-related deaths, according to the latest figures from the Department of Health and Social Care.

The number - updated daily - is the only official statistic available for the whole of the country.

It is updated every 24 hours and allows us to see the day-on-day change in the total deaths reported so far, as well as whether the rate is increasing or slowing down.

But it does not give us a real-time snapshot of the number of deaths in Covid-19 patients in the UK - nor is it an accurate reflection of exactly where we are in the "curve" of the outbreak.

As of 5pm on Sunday, March 29, 1,228 people in the UK had died after testing positive for the virus. Credit: PA Graphics

There a number of reasons for this, firstly the numbers that are published each day include deaths that have occurred over a range of dates.

This is usually over the previous few days, but can sometimes be from weeks earlier.

For example, the list of deaths announced by NHS England on March 29 included deaths that were recorded as taking place as far back as March 16.

This is because a death is only included in the figures once families of the victim have been informed.

Advising customers to keep two metres apart in shops is one of the social distancing measures. Credit: PA

As a result, the day-on-day change in the official death figures is not moving in step with how many coronavirus-related deaths are taking place in real time.

A second reason is because deaths included in the official total are focused only on those that have taken place in hospitals in England, Scotland, Wales and Northern Ireland.

These provide the most immediate sources of data for the Department of Health - which are then used for the daily updates.

As an example - NHS England publishes a daily breakdown of coronavirus-related deaths in England by NHS Trust.

Because of this, deaths that have occurred in the wider community - not in hospitals - are not included.

A convoy of military vehicles drive up the M6 as the UK continues in lockdown to help curb the spread of the coronavirus. Credit: PA

Elsewhere the Office for National Statistics (ONS) publishes weekly provisional figures on the total number of deaths registered in England and Wales - including the wider community - as well as whether the underlying cause of death is a respiratory disease.

There is, however, a lag in these figures of around 11 days.

The latest ONS figures, published on March 24, had numbers up to the week ending March 13.

These figures are also based on when a death is registered and not when it occurred.

The ONS has said that from March 31 onwards, its weekly update on deaths in England and Wales will include a separate breakdown of the number of deaths involving coronavirus.

It will specifically include in its breakdown the number of deaths where Covid-19 is mentioned anywhere on the death certificate.

The Government has introduced a whole host of measures to try and 'flatten the curve' of cases. Credit: PA Graphics

A third reason the official death figures do not give a real-time snapshot of where we are in the "curve" of the outbreak is due to the amount of time that can pass between somebody contracting the virus and them dying as a result of a virus-related issue.

As a result of this, any steps taken to limit the spread of the virus - such as social distancing or lockdowns - take time to show up in the number of deaths.

A study published in The Lancet on March 12 (based on data reported in Wuhan, China) found that the median average time from the onset of coronavirus symptoms to admission to an intensive care unit (ICU) is about 10 days.

A paramedic in personal protective equipment exiting an ambulance in London. Credit: PA

A separate study by the Intensive Care National Audit and Research Centre looked at cases in England, Wales and Northern Ireland up to March 26.

Researchers found that - of a sample of 165 patients treated in ICUs where an outcome was reported - 79 (48%) had died and 86 (52%) had been discharged.

Those who had died had spent a median average of four days in an ICU between the date of admission and the date of death.

Intensive care units across Europe have been under strain as a result of the outbreak. Credit: AP

These factors - the onset of symptoms and the time it takes for a patient to die while in hospital - adds another element to the lag in the death statistics.

Taken as a whole, these factors mean that we are likely to have to wait at least a couple of weeks to get a clear idea of whether measures introduced to try and "flatten the curve" of virus-related deaths in the UK have had an impact.

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