England and Wales have seen 27,000 more deaths than expected since the start of the Covid-19 outbreak.

New figures from the UK’s Office for National Statistics show there were more than twice as many deaths in the week ending 17 April than would have been expected in an average year.

A total of 22,351 people died during the week – more than twice the 10,497 seen across the previous five years. Those 11,854 excess deaths are the highest recorded in a single week and take the total since the start of March to 27,015.

Only 19,093 of the 27,015 excess deaths have been officially attributed to Covid-19. That leaves a gap of 7,922 deaths which are officially “unexplained” but are likely to be associated with the virus – either as a direct cause, or because the lockdown has restricted access to other forms of health and social care.

Of the “official” Covid-19-related deaths, 8,758 of these deaths were registered in the week to 17 April alone – the last week for which data is available.

That still leaves a large proportion of the 11,854 excess deaths during the week unexplained.

The chart below shows the number of weekly deaths during January to early March was fairly close to expected, if a bit lower.

Starting on the week ending 27 March however, the total number of deaths, both attributed to coronavirus and not, skyrocketed to more than double the expected level.

How do we measure Covid-19 deaths?

The exact number of deaths caused by Covid-19 is difficult to pinpoint.

The numbers in the chart above come from an ONS report that counts the number of death certificates released weekly in England and Wales where Covid-19 was mentioned anywhere on the death certificate, even in combination with other health conditions. The ONS data also includes deaths that occurred outside hospitals, such as in care homes.

The ONS also releases the daily number of Covid-19 deaths based on the actual date of death, rather than when the death was registered. This has the advantage of showing a more accurate picture at the expense of taking longer to record.

In addition, the Department of Health and Social Care also releases numbers for Covid-19 deaths on GOV.UK. These figures are updated daily and are based on the number of deaths in hospitals that are officially attributed to Covid-19.

While the ONS figures catch far more Covid-19 deaths, they don’t capture all the excess deaths we are seeing – suggesting we still don’t have the full picture of how, where, and why Covid-19 is killing people.

The reason we use the weekly ONS data based on the number of death certificates that mention Covid-19 is because it is the only count that allows us to put the number of deaths linked to coronavirus in the context of overall deaths and the numbers of deaths from previous years.