How might we know when UK coronavirus deaths have peaked?

Boris Johnson has started to unveil his road map for England's coronavirus lockdown exit strategy, a week after confirming Britain has "passed the peak" of Covid-19.

It comes after scientists confirmed the peak in the number of coronavirus deaths in England and Wales happened on April 8.

The death rate had been consistent for the first half of April, a panel convened by the Science Media Centre said about the data released by the Office of National Statistics (ONS) last month.

Prof Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford, said: "From an epidemiological perspective we can say that the numbers are consistent with the peak happening on April 8.

"We’ve now tracked for 13 days that that has been consistent – it hasn’t jumped up."

Knowing when the number of new coronavirus-related deaths in the UK has peaked is a key measure in understanding how we are doing in tackling the pandemic.

NHS England publishes figures every day that show the number of deaths in hospitals in England, together with the date on which they occurred.

It is one of the most valuable sources currently available for understanding when coronavirus-related deaths are taking place – even though the figures are only for deaths in hospitals in England where a patient has been tested for Covid-19.

They allow us to analyse changes in the number of deaths based on when the death actually occurred, not when the death was reported.

A graph showing the number of coronavirus-related deaths in hospitals in England. Credit: PA Graphics

This gives us a good indicator of the day-to-day growth in the number of deaths – and so provides a clue as to whether growth is accelerating, flattening or even slowing down.

So far April 8 has seen the highest increase in the total number of deaths: 771.

The reason we need to treat these figures with caution is because they are updated and revised every day, to incorporate deaths that have taken several days or even weeks to be confirmed.

For example, in the figures published by NHS England on April 12, the number of deaths recorded as occurring on April 11 was 121.

This number was then revised upwards to 443 in the bulletin published on April 13, to 575 on April 14, and to 637 in April 15’s bulletin.

NHS England publishes figures every day that show the number of deaths in hospitals in England, together with the date on which they occurred. Credit: PA

The number may be revised further in future updates.

In April 15’s bulletin, 15 dates have had their totals revised since April 14’s bulletin, which gives a sense of just how much of a lag there can be in aggregating the figures.

Reasons for the lag include the time it takes for deaths to be confirmed as testing positive for Covid-19, for post-mortem tests to be processed, and for data from the tests to be validated.

Yet even with these delays, the figures remain one of the most useful sources for analysing the dates of when coronavirus-related deaths are taking place.

Nine out of 10 coronavirus deaths takes place in a hospital setting. Credit: PA

The total for April 8 has remained the highest now for the past month, despite the daily revisions.

This will be the next test: whether the peak on April 8 is the one and only peak of the pandemic, or whether further peaks are on their way.

Crucial will be whether the number of deaths per day continues to fall during the next few weeks.

If the number plateaus, or even starts to rise, it could suggest a second wave of infections and deaths is approaching.

Coronavirus: Everything you need to know